The BBC is reporting that a van struck 15 to 20 pedestrians on London Bridge, the historic bridge spanning the Thames River in London.
Armed police are on the scene.
More information on this story as it develops.
UPDATE (6:05 p.m. Eastern): Witnesses are reporting multiple bodies scattered on the pavement. Reports include bursts of gunfire and victims suffering from stab wounds.
UPDATE (6:35 p.m. Eastern): Witness reports that heavy gunfire preceded the incident.
A witness says he heard "significant gunfire" which "went on for quite a few minutes" https://t.co/DdFVL0UmC9— Sky News (@Sky News)1496528400.0
UPDATE (6:43 p.m. Eastern): The Guardian is publishing reports of a second, possibly related incident at London's Borough Market.
The Guardian also published an image of what is believed to be the vehicle used to run down pedestrians.
UPDATE (6:53 p.m.): Police are evacuating bars, hotels and other businesses in the area of the attacks.
London bridge bar now. Police everywhere https://t.co/0gWH9jhgdX— James Yates (@James Yates)1496527594.0
Reuters reports that police are looking for three armed suspects:
BREAKING: UK police searching for three suspects who may be armed after 'major incident' on London Bridge - BBC… https://t.co/sx7eKiICgW— Reuters (@Reuters)1496529718.0
UPDATE (7:09 p.m.): Police are reporting on a third incident in London's Vauxhall area.
UPDATE (8:00 p.m.): London police have officially declared the attack a terrorist incident.
At 0025hrs 4/6/17 the incidents at #LondonBridge & #BoroughMarket were declared as terrorist incidents.— Metropolitan Police (@Metropolitan Police)1496533832.0
However, the Vauxhall incident is no longer believed to be related to the London Bridge and Borough Market attacks.
The incident at #Vauxhall is a stabbing and is not connect to the incidents at #LondonBridge & #BoroughMarket— Metropolitan Police (@Metropolitan Police)1496533888.0
President Donald Trump took to Twitter to complain that courts have overturned his anti-Musim travel ban.
We need to be smart, vigilant and tough. We need the courts to give us back our rights. We need the Travel Ban as an extra level of safety!— Donald J. Trump (@Donald J. Trump)1496531833.0
Watch live coverage of the incident, embedded below: