London: A 75-year-old man died on Thursday evening following the Westminster attack, taking the death toll to five, including the attacker, police said.
His next of kin have been informed and are receiving support from specially trained family liaison officers, BBC quoted Scotland Yard as saying.
On Wednesday, at least 40 people were hit on the iconic and crowded Westminster Bridge when the attacker drove a car along the pavement, knocking down unsuspecting pedestrians before crashing into a fence below Big Ben.
He then stabbed Police officer Keith Palmer who tried to stop the attacker in a courtyard outside the Houses of Parliament.
The Islamic State claimed responsibility for the attack. It said the attacker was "a soldier ... executing the operation in response to calls to target citizens of coalition nations".
The attacker was identified by police as Khalid Masood who was shot dead at the scene.
The other victims were identified as Aysha Frade and US tourist Kurt Cochran.
Kurt Cochran from the US state of Utah was in London as part of a holiday in Europe to celebrate 25 years of marriage to his wife Melissa, who was seriously hurt in the attack.
US President Donald Trump paid tribute to Cochran on Twitter, saying: "A great American, Kurt Cochran, was killed in the London terror attack. My prayers and condolences are with his family and friends."