LONDON - Metropolitan Police said seven people died in two terrorist incidents on London Bridge and Borough Market, in addition to the three suspects who were fatally shot by police. 

The events unfolded around 10 p.m. GMT when a van mowed down pedestrians along the London Bridge, police said. Police said three suspects exited the vehicle at the nearby Borough Market and attempted to stab people. 

The three suspects, who were wearing hoax suicide vests, were shot and killed by police. Live updates below:

8:25 a.m. ET: British police say they have arrested 12 people in east London over the London Bridge attack. Police said in a statement that counterterrorism officers made the arrests Sunday morning in Barking.

Police say the investigation is progressing rapidly.    

A British Transport Police officer and an off-duty officer were among the injured in the Saturday night attack.

7:53 a.m. ET: U.S. President Donald Trump tweeted about the London attack. 

"Do you notice we are not having a gun debate right now?" he tweeted. "That's because they used knives and a truck!"

Saturday night, the BBC reported at least one person had died and a witness who was on the bridge told the BBC she saw a speeding van veer onto the pavement, striking as many as six people. Police then responded to reports of incidents at two more sites. Live updates are below:

10:53 p.m. ET: Metropolitan Police Assistant Commissioner Mark Rowley gave an update on the incident, saying that the incident was a "protracted incident" that began on London Bridge and continued to Borough Market. 

He said that six people died in the incident in addition to the three attackers shot dead by police. There were at least 20 people wounded. 

The three attackers were wearing what appeared to be explosive vests, but it was determined to be a hoax, Rowley said. 

9:39 p.m. ET: London Ambulance Services said it has taken at least 20 patients to at least six hospitals. 

9:28 p.m. ET: A photo circulating on social media shows a man lying on the ground with canisters attached to his belt.  

8:43 p.m. ET: London Ambulance Services tweeted they are responding to the incident, posting that they had responded within six minutes of the initial reports.

8:39 p.m. ET: London Mayor Sadiq Khan describes bridge area incidents as "deliberate and cowardly attack on innocent Londoners."  

8:26 p.m. ET: The U.S. Department of Homeland Security issued a statement saying they are "monitoring" the situation in Britain.

'We are working with our interagency partners and foreign counterparts to gain further insight into reported attacks against civilians on London Bridge and in the surrounding area," the statement read. "U.S. citizens in the area should heed direction from local authorities and maintain security awareness. We encourage any affected U.S. citizens who need assistance to contact the U.S. Embassy in London and follow Department of State guidance."

8:22 p.m. ET: Australian Labor Sen. Sam Dastyari was eating at a restaurant near London Bridge during the attack.

"Terrible events in London beside where we were having dinner. Just terrible. Whole city in lockdown," he tweeted Saturday. "London police are amazing, had us in lockdown then evacuated us past the site. Horrific scenes."

8:07 p.m. ET: Police say they are working with Royal Naval Lifeboat Institution to evacuate public from the London Bridge incident.

British police are responding to three incidents across London following reports of a vehicle slamming into pedestrians on the London Bridge. Police say there is more than one fatality following the three separate incidents, the BBC reports. 

A witness who was on the bridge told the BBC she saw a speeding van veer onto the pavement, striking as many as six people. Police then responded to reports of incidents at two more sites. Live updates are below:

7:51 p.m. ET: Metropolitan Police tweeted the London Bridge and Borough Market incidents were declared terrorist incidents. The Vauxhall stabbing is not connect to the incidents, they tweeted. 

7:39 p.m. ET: Prime Minister Theresa May said the "terrible incident" is being treated as "potential act of terror."

Downing Street says May will chair a meeting of the government's emergency response committee on Sunday.  A spokesman for May says the prime minister is in contact with officials and is being regularly updated.

7:24 p.m. ET: President Trump tweeted the U.S. needs "the Travel Ban as an extra level of safety!" after the incidents in London.

The Metropolitan Police said on Twitter they responded to reports of a collision on the bridge shortly after 11 p.m. local time, followed by reports of a stabbing at Borough Market. Armed police responded and shots were fired, police said. Police further said armed officers were responding to a third incident in the Vauxhall area. 

The BBC reports police are searching for three suspects who could be armed, according to Reuters.

British Prime Minister Theresa May has been briefed on the incident and is in touch with officials, Downing Street said. White House press secretary Sean Spicer said President Trump has also been briefed on the situation.

President Trump responded to the incident with a message of support on Twitter. "Whatever the United States can do to help out in London and the U.K., we will be there," he tweeted. "WE ARE WITH YOU. GOD BLESS!"

The city transit authority Transport for London closed the bridge and ordered the London Bridge underground station evacuated.

One witness inside the station described the scene to Sky News. 

"I was walking out of the London Bridge station and there were police," Caroline Breniere said. "Some of them were coming by car, some of them were running. The traffic was stopped."

Another man who was nearby told Sky he witnessed emergency vehicles rushing to the scene.

"We finished drinking at a bar and we came out onto the road and I looked to my left and there was a guy, we thought he was just drunk, he was lying on the floor," the man told Sky. "A couple seconds later, about three police vans flew past. The guys who were with the guy that was on the floor managed to flag one of the police vans down. One of the officers jumped out and started attending to the guy on the floor."

Will Haven, managing editor of The Spectator in London, told Sky he "certainly saw people who looked like they'd been run over."

On March 22, a knife-wielding man mowed down pedestrians on London's Westminster Bridge before fatally stabbing an armed police officer to death just inside the gates of Parliament. Five people were killed, including the attacker, and at least 40 people were injured.

A State Department spokesperson said U.S. officials are closely monitoring the incidents in London.

"Our thoughts are with the family and friends of those affected by this terrible situation," the spokesperson said in a statement to CBS News. "We stand ready to provide all possible consular assistance should we become aware of any affected U.S. citizens." 

This is a developing story and will be updated.

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