More than one person has died in a terrorist incident in central London which is still ongoing, police have said.
Armed officers and ambulances were alerted to reports a van hit people on London Bridge shortly after 22:00 BST.
Police later went to nearby Borough Market where they were responding to reports of stabbings in the area which is known for its restaurants and bars.
Prime Minister Theresa May described the incidents as "dreadful events".
The Metropolitan Police tweeted: "At 0025hrs 4/6/17 the incidents at #LondonBridge & #BoroughMarket were declared as terrorist incidents."
London Mayor Sadiq Khan said it was an "horrific terrorist attack".
He added: "The situation is still unfolding and I would ask all Londoners and visitors to our city to remain calm and vigilant.
"We don't yet know the full details, but this was a deliberate and cowardly attack on innocent Londoners and visitors to our city enjoying their Saturday night. I condemn it in the strongest possible terms."
Witnesses report hearing gunshots in the Borough Market area while one social media user has posted a photograph appearing to show one of the attackers, with what seemed to be canisters strapped to his body lying on the ground.
