4 Dead, Including 1 Police Officer in London Attack

Four people are dead and at least 20 are injured from an attack in London that authorities have declared a terrorist incident. A police officer and the man believed to be the attacker are among the dead.

The attack began when the driver of a car struck bystanders and three police officers on the Westminster Bridge, London’s Metropolitan Police said. The car then crashed near the Houses of Parliament and at least one man armed with a knife attacked an armed officer who was guarding Parliament, police said.

The suspected attacker was shot by police.

French students were among the injured, according to French officials. A seriously injured woman was pulled from the River Thames and is receiving medical treatment, an official with the Port of London Authority told ABC News. Tobias Ellwood, a member of Parliament, was seen giving first aid to one of the victims.

Authorities said they received several different reports today, including a person in the River Thames, a car involved in a collision with pedestrians and a man armed with a knife.

David Lidington, leader of the House of Commons, told members of Parliament that a police officer was stabbed and an alleged assailant was shot by police.

Lidington added that there were reports of further violence in the area.

An eyewitness told the BBC that someone driving a car on Westminster Bridge appeared to hit bystanders.

At least 10 patients on Westminster Bridge had been treated, according to the London Ambulance Service.

Witness Richard Tice told ABC News that he saw injured people on the pavement. According to Tice, the car appeared to have jumped the curb, knocking people over.

The Metropolitan Police’s current acting commissioner, Craig Mackey, is a “significant witness as he was at the scene when the incident started,” and he was not injured, police said.

Police said additional officers are being deployed across London today and the public is asked to remain vigilant.

Parliament was placed on lockdown today after the attack.

As police swarmed the area, Tom Peck, a British journalist, told ABC News that he heard a loud bang, lots of screaming and then several gunshots from his office in London.

U.S. Secretary of State Rex Tillerson said in a statement, “I express my condolences to the victims and their families. The American people send their thoughts and prayers to the people of the United Kingdom. We condemn these horrific acts of violence, and whether they were carried out by troubled individuals or by terrorists, the victims know no difference.”

This story is developing. Please check back for more updates.

ABC News’ Kelley Robinson contributed to this report.