伦敦袭击后英国领导人态度坚定

British Prime Minister Theresa May struck a defiant tone after an attacker killed four people and injured about 40 others near Britain's Parliament in London, saying people should go about their business as usual Thursday.

"They will board their trains, they will leave their hotels, they will walk these streets, they will live their lives and we will all move forward together, never giving in to terror and never allowing the voices of hate and evil to drive us apart," May said.

The prime minister added that lawmakers would hold their normal meeting Thursday.

But London is under extra security with a boost in both armed and unarmed officers as police continue to investigate the attack that began Wednesday with a car running into pedestrians on Westminster Bridge.

Mark Rowley, head of counterterrorism efforts for London's Metropolitan Police Service, said authorities believe they know the attacker's identity, but are not yet releasing that information.

"We have hundreds of officers on this investigation and they are focusing on the suspect's motivation, preparation and his associates," Rowley told reporters.

He said authorities are working on the assumption that the attack was an act of "Islamist-related terrorism."

Rowley also identified the security officer who died in the attack as 48-year-old Keith Palmer, a husband and father who had served in British law enforcement for 15 years.

Prime Minister May addressed the public on television, calling the attack "sick and depraved."

May said any attempt to intimidate the British people through violence and terror is doomed to failure.