A British police officer stands guard outside Parliament after an apparent terrorist attack Wednesday.

LONDON (Diya TV) — An assailant fatally stabbed a police officer at the gates of Britain’s Parliament compound and a vehicle plowed through a crowd of terrified people along a landmark bridge Wednesday in what authorities have designated as a “terrorist incident.”

The suspected attacker was shot amid a sleuth of casualties in some of the most famous streets in central London.

Bodies laid on the Westminster Bridge over the River Thames as a Foreign Office official, bloodied by the attack on his counterpart, tried to save the life of the slain officer. British media later reported the police officer died, a hospital official later said at least one civilian had been killed.

Meanwhile, authorities tried to piece together the sequence of events in an attack on one of the city’s most highly protected sites. Questions such as whether the incident at Westminster Bridge was part of a more coordinated strike that employed elements of previous terrorist attacks needed immediate attention — vehicles were used in attacks in Nice and Berlin last year.

“We are treating this as a terrorist incident until we know otherwise,” said a Twitter message from London Metropolitan Police.

Britain’s Press Association news agency, citing a doctor at a London hospital, said one woman was killed and other people were under medical treatment. The report could not be independently verified. Metropolitan Police Cmdr. B.J. Harrington said there were “a number of casualties including police officers,” but did not give further details or figures.

The attack took place during Parliament’s busiest day of the week, when the prime minister makes her weekly appearance at the House of Commons in front of a capacity crowd of visitors. The Palace of Westminster, the ancient seat of the British Parliament, is surrounded by heavy security, with high walls and an ample supply of armed guards. But just outside the compound are London’s busy streets, packed with cars and pedestrians.

Britain has been on high alert for terrorist attacks for several years, top security officials have for some time been warning that a strike was all but inevitable. Until Wednesday, the country had been sparred from such incidents like the ones that have taken place in France, Belgium and Germany in recent years.

French Prime Minister Bernard Cazeneuve said that among those wounded in the vehicle attack were a group of French students.

A nearby hospital was put on lockdown and the London Eye — the enormous Ferris wheel above the River Thames — was stopped and visitors were slowly let off hours later. Those who were locked inside the Eye’s capsules at the time of the attack were kept there. In a brief news conference just before 5 p.m. outside the nearby headquarters of Scotland Yard — London’s police force — a spokesman said he was “not going to speculate” on whether the incident was over.

The Department of Homeland Security said it was in “close contact with our British counterparts to monitor the tragic events and to support the ongoing investigation.” It noted that U.S. security threat levels remained unchanged.

One year ago to the day, attackers carried out three coordinated suicide bombings in Belgium, killing 32 civilians and injuring more than 300 others in two blasts at Brussels Airport and one at a metro station in the Belgian capital. The Islamic State claimed responsibility for those attacks.