The police officer killed in a terror attack at Westminster today (22 March) has been named as PC Keith Palmer. The 48-year-old was unarmed as he was fatally stabbed by an attacker near the Houses of Parliament.

Foreign Office minister Tobias Ellwood, who was at the scene as the horrifying incident unfolded, attempted to give mouth-to-mouth resuscitation to the fallen police officer. However, PC Palmer's injuries were too severe and he died at the scene. The attacker was shot dead by police.

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PC Palmer was a member of the Met's parliamentary and diplomatic protection command and had 15 years service. He was married with children.

Acting Deputy Commissioner and head of counter-terrorism at the Metropolitan Police, Mark Rowley, paid tribute to PC Palmer, saying: "He was someone who left for work today expecting to return home at the end of his shift - and he had every right to expect that would happen."

Four others, including the attacker, are also confirmed dead and at least 40 other people were injured after a car struck pedestrians on nearby Westminster Bridge before it crashed. Eyewitnesses described scenes of panic and carnage on the streets of London in the aftermath of the attack.

Three police officers were among those injured, two of whom are in a serious condition, while some of the pedestrians are said to be in a critical condition.

Rowley confirmed that the attacker was known to police and was believed to be inspired by international terrorism.

PC Keith Palmer
PC Keith Palmer was fatally stabbed by a terrorist in the grounds of the Houses of Parliament Met Police Handout

Speaking in Downing Street after chairing a meeting of the government's Cobra emergencies committee, Prime Minister Theresa May said it was a "sick and depraved" attack on the heart of the capital and attempts to defeat UK values were "doomed to failure".

May paid tribute to the "exceptional men and women" of the police force who responded to the attack, saying: "We will all move forward together, never giving in to terror and never allowing the voices of hate and evil to drive us apart."

The prime minister said the UK terror threat level would remain at severe - its second highest - meaning an attack is "highly likely", BBC News reports.

Members of the public have turned to social media to express their shock at the attack in the heart of the capital and to pay tribute to PC Palmer.

Counter-terrorism police unit tweeted: "Our thoughts are with the family of PC Keith Palmer@metpoliceuk a husband, a father and a colleague."