LONDON — British police late Thursday arrested a man and a woman in connection with the butchering of a British soldier on a London street, as anti-Muslim protests sprang up across the country.
The arrests fueled speculation that the gruesome knife attack Wednesday — the first successful terrorist act in Britain since 2005 — was part of a wider plot, and prompted questions about the prevalence of Islamic extremism in the country and how to combat it.
British officials moved quickly to increase security in London and other major cities Thursday as police raided homes and searched for clues at the crime scene.
Police said they had arrested a man and woman, both 29, on charges of conspiracy to murder. Police did not identify these suspects or indicate whether more arrests in the case were imminent.
Meanwhile, British military officials identified the slain soldier as Drummer Lee Rigby, 25, a machine-gunner in the 2nd Battalion, the Royal Regiment of Fusiliers. A father of a 2-year-old boy, Drummer Rigby joined the army in 2006 and served in Afghanistan before becoming a recruiter with duties in the Tower of London.
Wednesday afternoon, Drummer Rigby was off duty as he walked near the Royal Artillery Barracks in the southeast London neighborhood of Woolwich when he was hit by a blue car.
Two men got out of the car and held him against a wall, then stabbed and decapitated him with kitchen knives and a meat cleaver, according to British media reports. The two men threw his body into the street.
One of the men — identified by former associates as Michael Adebolajo, a Christian convert to Islam who is believed to be a second-generation Nigerian Briton — stopped to explain his actions to a bystander making a video recording.
"I apologize that women had to witness this today, but in our lands our women have to see the same," he said to the camera while holding a knife and a cleaver in his bloody hands. "You people will never be safe. Remove your governments. They don't care about you."
Both men remained on the scene until police arrived and were shot in the leg after attacking the officers. They were being held in separate hospitals under armed guard, and one of them was reported to have serious injuries.
The grisly attack was the first successful Islamist-inspired assault in the United Kingdom since the July 2005 bombings on the London transportation system that killed 52 people.
Questions are arising over the effectiveness of the security measures after the 2005 bombings, especially as British security services acknowledged that they were aware of the pair involved in Wednesday's slaying. Officials offered no details about whether the two suspects were under recent surveillance.
Prime Minister David Cameron and opposition leader Ed Miliband cut short trips to France and Germany, respectively, in response to the slaying. On Thursday morning, Mr. Cameron led an emergency response committee meeting to discuss security measures.
Later with London Mayor Boris Johnson, Mr. Cameron met with community leaders and defended British Muslims.
"This was not just an attack on Britain and on the British way of life; it was also a betrayal of Islam and of the Muslim communities who give so much to this country," the prime minister said. "There is nothing in Islam that justifies this truly dreadful act."
The Muslim Council of Great Britain condemned the killing, calling it a "truly barbaric act."
"This action will no doubt heighten tensions on the streets of the United Kingdom," the council said. "We call on all our communities, Muslim and non-Muslim, to come together in solidarity to ensure the forces of hatred do not prevail. It is important we allow our police authorities to do their job without speculation."
Wednesday night, Tommy Robinson, leader of the far-right English Defense League, led an anti-Muslim march through Woolwich that resulted in violent scuffles with residents.
Mosques were the targets of attempted attacks in the towns of Braintree and Gillingham, just outside London.
Londoners expressed anger Thursday over the soldier's slaying, but some said they didn't blame Islam or British Muslims for the attack.
"It's not terrorism but a brutal murder using that as an excuse," said Jordan Blackman, a builder.
Others expressed shock.
"It's one thing to be killed in action abroad, but for something like this to happen in your own country and on the streets of the capital is just disgusting," said Rob Bryfield, a construction worker. "I don't think it's terrorism, though. They just say [that] on the news to scare us."
On Thursday, a Muslim hard-liner said publicly that Mr. Adebolajo took part in demonstrations with the banned radical group al-Muhajirounoun.
Omar Bakri Muhammad, who is in Lebanon but once was a radical Muslim preacher in London, told The Associated Press that Mr. Adebolajo was a "shy person" who was keen to learn about Islam.
"I was very surprised to learn that he is the suspect in the attack," Mr. Muhammad said.
Security officials have been increasingly concerned over British nationals, especially converts to Islam, becoming "lone wolf" extremists. Dozens of Britons have been questioned for seeking out Islamist training and trying to fight for jihad overseas.