LONDON (Reuters) -- A knife attacker slashed a man at an east London metro station, reportedly screaming "this is for Syria," in what police described as a terrorist incident, prompting the government to urge Britons on Sunday not to be intimidated by the attack.
A pool of blood near the ticket barriers at the Leytonstone Underground station, about six miles (10 km) east of central London, could be seen in footage posted on Twitter that also showed the suspect confronting police officers on Saturday evening.
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Police said initial reports indicated the man, believed to be aged 29, had also threatened other bystanders. One 56-year-old man suffered serious but not life-threatening injuries. Two other people had minor injuries, police said.
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The man was arrested after police discharged a Taser which stuns suspects.
An eyewitness quoted by The Guardian and other British newspapers said the attacker appeared to claim that he was retaliating for Western air strikes on Islamist militants in Syria. Police declined to comment on those reports and it was not immediately possible to verify them independently.
British war planes joined the strikes on targets in Syria for the first time on Thursday, a few hours after parliament had approved the involvement.
Senior government minister Iain Duncan Smith said whatever the circumstances, Britons must not let the Leytonstone incident affect their behavior.
"We cannot let these sort of people, terrorists et cetera, actually dominate our space," he told the BBC. "The way we defeat them at the end of the day is with our values, our freedom of expression, our freedom of belief ... our ability to take our children, our families out at Christmas. None of that must be curtailed."
Nevertheless, the attack will draw parallels with the May 2013 murder of British army soldier Lee Rigby, who was hacked to death just south of the Thames River by two Muslim converts.
Britain is on its second-highest alert level of "severe," meaning a militant attack is considered highly likely, mainly because of the threat posed by Islamic State militants in Syria and Iraq who are encouraging supporters to attack the West.
Prime Minister David Cameron won parliamentary approval to bomb the Islamist State group in Syria after the group claimed responsibility for the attacks on Paris last month that killed 130 people.
In an interview with the Sunday Times newspaper, Syrian President Bashar al-Assad mocked Cameron's strategy in the region, saying it would make the situation worse, not better.
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THREAT TO BRITAIN?
Cameron said air strikes would not increase the chances of an attack on Britain, since militants already viewed the country as a top target with seven plots foiled over the past year.
An eyewitness to the knife attack was quoted as saying the attacker had screamed about Syria. "As he was coming out this is what he said: 'This is what happens when you f*** with mother Syria, all of your blood will be spilled'," the Guardian quoted an eyewitness as saying.
Two years ago, Michael Adebolajo and Michael Adebowale ran over Fusilier Rigby near Woolwich Barracks before setting upon him with knives and a meat cleaver in an attempt to behead him. They were jailed for life last year.
British security services say about two-thirds of their time is spent countering international militants, much of that connected to Syria.
Britain's worst militant Islamist attack was in July 2005, when 52 people were killed by suicide bombs on underground trains and a bus.
Islamic State said on Saturday that the married couple who killed 14 people in a mass shooting in California, which U.S. authorities are investigating as an act of terrorism, were followers of the militant group.
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