At least six people died and three attackers were killed in multiple "terrorist incidents" Saturday in London after a van plowed into pedestrians on London Bridge and assailants went on a stabbing rampage at nearby Borough Market, police say.
London Ambulance Service said they had taken at least 30 patients to six hospitals, and treated a number of people at the scene with less serious injuries.
Mark Rowley, head of counter-terrorism for Metropolitan Police, said police believe all of the attackers were killed, but investigations are underway to ensure there are no more.
Police said in a tweet that "the incidents at #LondonBridge & #BoroughMarket were declared as terrorist incidents" and appeared to be connected.
Earlier, Prime Minister Theresa May said the attacks were being investigated as a "potential act of terrorism."
The first incident took place just after 10 p.m. on London Bridge, where witnesses described seeing a white van mounting the sidewalk and plowing into pedestrians. A BBC reporter who was on the bridge at the time said the van was being driven at around 50 mph by a male suspect.
Police say the van continued on to Borough Market, a nearby area that houses many food stalls and pubs and is popular with tourists. Police say the suspects jumped out of the van and stabbed pedestrians and an off-duty British Transport Police officer. The officer suffered serious but non-life threatening injuries, police say.
Responding officers confronted three male suspects, who were shot and killed in market, police say. The suspects were wearing what looked like explosive vests but these were later established to be hoaxes.
"At this stage, we believe that six people have died in addition to the three attackers shot dead by police," Rowley said.
London Bridge, which crosses the River Thames in London, was closed in both directions.
During the attack, police urged people to flee the area. Shots were fired, however, it was not clear if the shots were fired by police or the assailants.
Police urged Londoners to be calm and vigilant and circulated a message that read: "Run," "Hide," "Tell."
There were also reports of a third incident, a stabbing in the Vauxhall area of London. That was subsequently said to be unrelated to the terror attack.
The British Prime Minister's office said May was being regularly updated on the situation, and the White House said President Trump has been briefed.
"Whatever the United States can do to help out in London and the U. K., we will be there - WE ARE WITH YOU. GOD BLESS!" Trump tweeted.
Reports of the incident reflected fear that the incident could be terrorism. Britain has weathered two terrorism attacks in recent months. In March, four people were killed in London after Khalid Masood rammed his car into pedestrians on Westminster Bridge before fatally stabbing a policeman outside the Houses of Parliament.
On May 22, a British-born suicide bomber killed 22 people and injured 59 others at an Ariana Grande concert in Manchester, England.
The attack came on the eve of a benefit concert Grande is scheduled to play in Manchester on Sunday in aid of the victims and their families.