Four people were killed while more than 40 were injured caused by an attacker who drove a car and ran through the crowds in central London. He then went on to try and storm the Houses of Parliament, believed to be an act of Islamist-inspired terrorism by the police.

An unarmed police officer Keith Palmer, who has served for 15 years was stabbed to death after the suspect rammed a car into the crowds by the sidewalks. Police pointed out that they are aware of the identity of the suspect after they shot him dead.

Prime Minister Theresa May said the attack was "sick and depraved", added that the attempts to defeat the values Parliament represents through violence would be "destined to failure."

"The location of this attack was no accident. The terrorist chose to strike at the heart of our capital city, where people of all nationalities, religions and cultures come together to celebrate the values of liberty, democracy and freedom of speech," she said.

The area around Westminster was filled with walkers when the attack happened at about 2:40 p.m. Witnesses said the attacker drove his car over Westminster Bridge and into the crowds. The vehicle hit a lot of civilians, including three police officers.

This was the first mass-casualty terrorist attack in Britain since 2005 when 52 people and four attackers died in the July 7 from the bomb attacks on the London public transport. The use of a vehicle as a weapon of terror is similar to the methods used by attackers in Nice and Berlin few years ago.

As reported by CNN, parliament was on lockdown for several hours and lawmakers were forced to stay in the main debating chamber of the House of Commons as officers went gushing to the scene outside.