PC Keith Palmer, aged 48 and a former soldier in the Royal Artillery, has been named as the police officer who was murdered in New Palace Yard, the courtyard in front of the Houses of Parliament.
A minute's silence was held nationwide at 09:33 GMT, including in the Palace of Westminster and at New Scotland Yard, to commemorate those who were killed in Wednesday's attack. The time for this morning's minute's silence was chosen in honour of murdered police officer Keith Palmer's shoulder number - 933.
Conservative MP Tobias Ellwood has been hailed a hero for attempting to resuscitate PC Palmer. Ellwood lost his brother in the 2002 Bali bombing.
Aysha Frade, 43, is the first member of the public to be identified as a victim.
The mother-of-two was reportedly crossing Westminster Bridge to collect her children from school when she was killed.
Aysha was Spanish-born but held a British passport.
Theresa May has just told the Commons that the terrorist was British-born.
Five people, including the terrorist, have been killed, and around 40 injured.
A woman with serious injuries, who was rescued from the River Thames, is believed to have either fallen from the bridge or jumped off to evade the attacker. A group of French students aged 15–16, from Concarneau in Brittany, were among those injured. Others included three police officers who were returning from a commendation ceremony, two Romanian citizens, and four students from Edge Hill University in northern England. Five South Koreans, an Australian, a Chinese and a Portuguese are also known to have been injured.
The French Foreign Minister Marc Ayrault is in the public gallery watching the proceedings in the Commons.
London attack: British-born attacker 'known to MI5'
BBC News
23 March 2017
The Westminster attacker was British-born and known to the police and intelligence services, the prime minister has revealed.
In a statement to the Commons, Theresa May said he had been investigated some years ago over violent extremism but had been a "peripheral figure".
"He was not part of the current intelligence picture," she said.
Eight arrests have been made following the attack on Wednesday that left four dead.
Those that died are PC Keith Palmer, Aysha Frade who worked at a London college, a man in his 50s and the attacker.
Seven of the injured are still in hospital in a critical condition.
A further 29 had been treated in hospital, Mark Rowley, the Metropolitan Police's Assistant Commissioner for Specialist Operations, said.
In the attack on Wednesday afternoon, a man drove a car along a pavement on Westminster Bridge knocking down pedestrians, creating panic and leaving dozens injured.
He then ran towards Parliament where he stabbed PC Palmer who was unarmed. Armed police then shot dead the attacker in the grounds.
Mrs May paid tribute to PC Palmer saying: "He was every inch a hero and his actions will never be forgotten."
Mrs Frade worked at a London sixth form college just a few hundred metres from Westminster Bridge.
Tel Aviv City Hall in Israel is lit up in the Union Jack to pay tribue to the victims
The Eiffel Tower in Paris turned off its lights at midnight
Principal at DLD College, Rachel Borland, said she was "highly regarded and loved by our students and by her colleagues".
PC Keith Palmer stopped the attacker in his tracks. Aysha Frade would be deeply missed by all, the principal at the college said
In an earlier statement made outside Scotland Yard, Acting Deputy Commissioner Mark Rowley said seven arrests had been made during raids in London and Birmingham - an eighth was announced several hours later.
"It is still our belief - which continues to be borne out by our investigation - that this attacker acted alone and was inspired by international terrorism.
"To be explicit, at this stage we have no specific information about further threats to the public."
He urged journalists not to publish the attacker's name while searches were continuing.
He said Londoners should expect to see more police officers on the streets, after officers' leave had been cancelled and duty hours extended.
It was initially thought that three members of the public had been killed on Westminster Bridge, but Mr Rowley referred to just two in his statement.
Director General of MI5 Andrew Parker condemned the attack as "appalling and disgusting".
The agency's operational response was "fully mobilised in support of the police", he said.
Met Police Acting Deputy Commissioner Mark Rowley gave update on the investigation early this morning
In other developments:
A witness told the Press Association that three men were arrested in an armed raid on a Birmingham address.
The BBC understands this is linked to the London attack
There is an unconfirmed suggestion that the car used in the attack was hired from an address in Birmingham, BBC Newsnight says
Security at Parliament will be reviewed, says Defence Secretary Sir Michael Fallon
The flag over the Houses of Parliament is flying at half mast
MPs held a minute's silence before Parliament continued business as normal
People worried about family and friends can call the police casualty bureau on: 0800 056 0944 or 0207 158 0010. Anyone with images or footage of the incident can send them to ukpoliceimageappeal.co.uk
MPs have held a minute's silence in Parliament before normal business resumes
Defence Secretary Sir Michael Fallon told BBC Radio 4's Today programme the "working assumption" was that the attack was linked to "Islamic terrorism in some form".
He paid tribute to Pc Palmer, a 48-year-old father and husband, and an unarmed member of the Parliamentary and Diplomatic Protection Squad who had served for 15 years.
Pc Palmer stopped the attacker getting into Parliament and "gave his life for the democracy we all cherish", he told BBC Breakfast.
Asked about the mood of the city, Sir Michael said: "London is getting back to normal. They've seen terrorism like this before and they are not going to let it triumph."
Brendan Cox, the husband of murdered MP Jo Cox, said it was important to remember that "this was a story about people who didn't come home yesterday".
US President Donald Trump was among world leaders to offer their support to Mrs May, tweeting: "Spoke to UK Prime Minister Theresa May today to offer condolences on the terrorist attack in London. She is strong and doing very well."
The Pope said in a letter to the Archbishop of Westminster that he had been "deeply saddened to learn of the loss of life and the injuries" and "assured the nation of his prayers".
Analysis
By Dominic Casciani, home affairs correspondent
The carnage on Westminster Bridge and inside the grounds of Parliament is the attack that security chiefs here in the UK have long been preparing for.
Terrorism looks not just to kill and maim - but to create panic and such a sense of disorder that it rocks a city or nation to its foundations.
And this attacker sought to do so in as low-tech way as is possible.
The days when terrorism meant large, complex bombs and months of planning are gone: Western security agencies - particularly MI5 and its partner agencies - are very, very good at identifying those plots and disrupting them.
The longer it takes to plan such an attack, the more people who are involved, the more chances there will be for security services to learn what is going on.
London attack: British-born attacker 'known to MI5' - BBC News