At least five people were killed and 40 others were injured outside the UK Parliament in London on Wednesday after an assailant drove a car into pedestrians and stabbed a police officer.

Britain's Press Association reported that a car barrelled into pedestrians along the sidewalk of Westminster Bridge, causing multiple "catastrophic injuries."

Police said they assumed the assailant had been “inspired by international terrorism.”

Driving a large SUV, the assailant slammed into pedestrians on Westminster Bridge near Parliament, killing two people and injuring dozens, before crashing into a fence.

After the crash, the driver left the vehicle and approached Parliament, where he stabbed an armed police officer to death and was fatally shot by the police.

It appeared to be the most serious such assault in London since the deadly subway bombings in 2005. No group or individual has so far assumed responsibility for the incident.

The Metropolitan Police said law enforcement personnel were called to the scene at around 2:40 pm, local time.

Police have arrested seven people in association with the attack and were investigating their possible ties to the assailant, who was identified as a reported Daesh sympathizer.

Daesh supporters on social media celebrated the deadly attack, with one user warning that “our battle on your land is only just beginning.”

The House of Commons session was suspended and members of parliament who were in the chamber were told to remain there.

UK Prime Minister Theresa May was rushed into a vehicle and spirited back to her office at 10 Downing Street.

She held a meeting of the government’s emergency committee and issued a statement on Wednesday night from her official residence condemning “the sick and depraved terrorist attack on the streets of our Capital this afternoon.”

May also said that “the full details of exactly what happened are still emerging,” but she confirmed that the attack had been carried out by a lone male assailant.

The Westminster incident took place on the first anniversary of attacks in the Belgian capital Brussels that left over 30 people dead and more than 300 others injured.