The police officer who was stabbed by a knife-wielding assailant inside the gates of the Houses of Parliament has died, despite Tory MP Tobias Elwood's attempt to save him.

The Tory MP was hailed as a hero after he rushed to the injured police officer's aid. The police officer was one of four people confirmed dead at this time. At least twenty people have been injured.

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He was seen attempting to give the police officer mouth-to-mouth resuscitation and stem the blood flow by applying pressure to his wounds, according to The Telegraph.

One eye-witness said: "He ran in opposite direction to everyone else, he ran towards the injured police officer."

Ellwood – a former soldier – lost his brother Jon in the Bali terror attack in 2002 that killed 202 people, including 27 Britons. He has been an MP for Bournemouth South since 2005 and most recently worked as parliamentary under-secretary at the Foreign Office.

Houses of Parliament
A police officer and a woman have been confirmed dead following a terror attack at the Houses of Parliament in Westminster, London Daniel Leal-Olivas/AFP

He remained with the injured officer while waiting for the air ambulance to arrive. The Telegraph's political respondent Christopher Hope said he saw Ellwood being comforted in the New Palace Yard after medical staff took over.

He was later seen with bloodied hands talking to police officers before he returned to the Foreign Office.

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