Police raided houses in connection with the brazen slaying of the off-duty solider, identified as Lee Rigby, of the 2nd Battalion The Royal Regiment of Fusiliers, who served in Afghanistan. In addition to the two suspects who were hospitalized after being shot by police, authorities said they had arrested a man and a woman, both 29, on suspicion of conspiracy to murder.
Police would not say whether it appeared Rigby had been targeted specifically because of his military service. Although he was not in uniform at the time he was killed, he was said by witnesses to be wearing a T-shirt for a British veterans' charity.
Anjem Choudary, the former head of the radical group al-Muhajiroun, told The Associated Press that the man depicted in startling video footage that emerged after Rigby's death was named Michael Adebolajo, a Christian who converted to Islam around 2003 and took part in several demonstrations by the group in London.
The BBC broadcast video from 2007 showing Adebolajo standing near Choudary at a rally.
Omar Bakri Muhammad, who now lives in Lebanon but had been a radical Muslim preacher in London, also said he recognized the man seen on TV as Adebolajo and said he attended his London lectures in the early 2000s.
Police have not identified either of the two wounded suspects and have not said when they would do so. Authorities in Britain usually wait to name suspects after they have been charged.
Bakri, speaking from Lebanon, said he remembers Adebolajo as a "shy person" who was keen to learn about Islam and asked interesting questions.
"He used to listen more than he spoke," Bakri said. "I was very surprised to learn that he is the suspect in the attack."
Mary Warder, who has lived in the Woolwich area for more than 30 years, told the AP said she had seen both of the suspects preaching on the streets. Shopkeepers, however, said they couldn't remember seeing them.
The two men suspected of killing the 25-year-old Rigby had been part of previous investigations by security services, a British official said Thursday, as investigators searched several locations and tried to determine whether the men were part of a wider terrorist plot.
There also was no clear indication on when or where the suspects may have been radicalized.
Rigby, the father of a 2-year-old boy, was slain Wednesday afternoon outside the Royal Artillery Barracks in the Woolwich area of south London while horrified bystanders watched in the busy city known for its decorum.
The bizarre scene was recorded on witnesses' cellphones, with one of the two suspects boasting of their exploits and warning of more violence as the soldier lay on the ground. Holding bloody knives and a meat cleaver, they waited for the arrival of police, who shot them in the legs, according to a passerby who tried to save the dying soldier.
A British government official said one of the two men tried to go to Somalia to train or fight with the terror group al-Shabab. The official, who spoke on condition of anonymity because he was not authorized to speak about the police investigation, would not say if the suspect had been arrested or whether he had made any other trips to the country.
Citing unidentified sources described as having "knowledge of British jihadis," the BBC's "Newsnight" program reported that one of the suspects in the attack was arrested last year on his way to joining al-Shabab.
Prime Minister David Cameron vowed that Britain would not be cowed by the horrific bloodshed, and that it would reject "the poisonous narrative of extremism on which this violence feeds." In Washington, President Barack Obama said the U.S. "stands resolute with the United Kingdom" in the fight against violent extremism.
There were few signs of alarm on the streets of London, which has been hit by terrorist attacks during a long confrontation with the Irish Republican Army and more recently, in July 2005, by al-Qaida-inspired suicide bombings that killed 52 commuters.
"It's hateful, it's horrific and upsetting. But it doesn't seem to have made much of a difference," Christian White, 43, said at King's Cross station, close to the site of one of the 2005 bombings. "Londoners are used to living in a city where life is complicated."
Even so, security was increased at military barracks and installations in the capital, with extra armed guards added in many cases. Police said extra patrols were added at sensitive areas, including places of worship, transport hubs and congested areas.
Both of the hospitalized suspects had been part of previous terrorism investigations by Britain's security services, according to a British official who spoke on condition of anonymity because he was not authorized to speak about the police inquiry and cautioned that details could jeopardize future trials.
It was unclear how recent the investigations were, whether the men were loosely tied to other suspects being investigated, or whether they themselves had been put under surveillance, which could have included being watched by undercover investigators or having their phone calls and emails intercepted.
Dramatic video showed a black man — animated, hands stained with blood and holding a meat cleaver — criticizing the British government and the presence of U.K. troops in foreign lands.
Maajid Nawaz, a former Islamist now with the London-based Quilliam anti-extremism think tank in London, said the video and emerging details indicated the men had been inspired by al-Qaida even though they may not have been directed by any specific affiliate to attack the soldier.
"There is always mood music playing before these attacks happen," Nawaz told the AP. "In this instance, I'm not saying they are operationally linked to al-Qaida, but these men clearly felt an affinity to this global jihadist zeitgeist. And they wouldn't have had to have visited any foreign countries for this ideology to have resonated with them."
Security officials have been worried over the recent increase of men seeking training and fighting opportunities in countries such as Syria, Somalia and Yemen.
Dozens of British men and women are said to have been radicalized by U.S.-born militant cleric Anwar al-Awlaki, the militant leader who was killed in a 2011 U.S. drone strike in Yemen.
A Twitter account used by members of Somalia's al-Shabab militant group made a lengthy post Thursday about the attack in Woolwich.
The Twitter account referenced a video of the bloodied suspect calling the attack "an eye for an eye" for what it called the British army's "woeful record of abuses" against Muslims worldwide.
"We swear by almighty Allah we will never stop fighting you," the man in the video declared, complaining about British troops fighting Muslims. "We must fight them as they fight us."
The camera then panned away to show a body lying on the ground. This video, with its venomous threats, may provide the lasting image of the tragedy.
Police in the eastern England county of Lincolnshire said a property was searched in connection to the Woolwich attack. Police said a search warrant had been obtained but would not provide details. Police were also scouring the attack site for further clues.
There also was a police raid on a public housing complex in east Greenwich just outside of London thought to be related to the investigation.
One man was arrested Wednesday outside a mosque in Essex after he threw a smoke bomb, police said. He was also found to be carrying knives and is expected in court Friday. No one was injured.
Separately, police in Kent said they charged a 45-year-old man with religiously aggravated criminal damage and burglary. The man, Andrew John Grindlay, was arrested Wednesday night.
There were no incidents reported at London mosques. Police called for the public to remain calm and said there were 1,200 officers deployed on the streets.
Britain's security threat remained the same since the killing, but security officials said they were reviewing preparations for next month's Group of Eight summit in Northern Ireland. Obama and other world leaders are expected to attend the meeting on June 17-18.
Police defended the speed of the department's response to the Wollwich attack. Assistant Commissioner Simon Byrne said police were on the scene nine minutes after receiving the first emergency call. Once it became clear that guns were involved, firearms officers were called and arrived 14 minutes after the first call to police, he said.
The Ministry of Defense said Rigby, who joined the army in 2006, was a machine gunner posted in Cyprus, Afghanistan and Germany before becoming a recruiter who assisted with duties in the Tower of London.
Nicknamed "Riggers," he was an important member of the Corps of Drums who was known for his good nature and wit, and his love of his hometown soccer team, Manchester United, according to fellow soldiers.
"He was one of the battalion's great characters, always smiling and always ready to brighten the mood with his fellow Fusiliers. He was easily identified ... on parade by the huge smile on his face and how proud he was to be a member of the Drums," Warrant Officer Class 1 Ned Miller said in a statement issued by the ministry.
Rigby's family said he would "do anything for anybody," always looked out for his sisters and took a "big brother" role with everyone he met.
"He was a loving son, husband, father, brother, and uncle, and a friend to many," the family said in a statement issued by the ministry.
Associated Press writers Cassandra Vinograd, Sylvia Hui, Matt Surman and Danica Kirka in London and Zeina Karam in Beirut contributed to this report.
Copyright 2013 The Associated Press.