The head of counterterrorism at London's Metropolitan Police, Mark Rowley said the dead policeman was among the armed officers who guard Parliament while the other victims died on Westminster Bridge after the attacker mowed down pedestrians in a car, leaving at least 20 people injured.
At least three other police officers were also injured in the attack.
A search is underway to make certain no other attackers are in the area though police believe there was only one attacker.
"We are carrying out a full investigation into the events. Our strength as a city is our ability to stand together. We will do all we can to protect the people of London," he added.
Also Read
Scotland Yard had earlier called on the public to "remain vigilant" andsaid a review of policing strategy across the city was underway, with additional police officers being deployed across London.
The Indian High Commission in London has set up a special "Public Response Unit" for any Indians caught up in today's terror attack.
Plainclothes armed officers shouted warnings at him before shooting a number of rounds.
He was later seen being covered by blankets, presumed dead.
UK Foreign Office minister Tobias Ellwood administered mouth-to-mouth resuscitation to the stabbed police officer but said he "died at the scene".
In an incident just minutes earlier, a speedinggrey Hyundai i40mowed down several pedestrians on Westminster Bridge nearby before ramming into the iron railings of the side of the House of Commons building.
Disclaimer: No Business Standard Journalist was involved in creation of this content