British officials on Saturday said they were responding to an incident on London Bridge, which spans the Thames River. The BBC said a van had hit a number of pedestrians on the bridge.
London's Metropolitan Police Service announced on Twitter that officers were on the scene. There were no immediate reports of casualties.
Last month, 22 people were killed and more than 59 others were injured in an explosion at an Ariana Grande concert in the British city of Manchester that police said was caused by a bomber carrying an improvised explosive device.
The explosion happened near an entrance to the 21,000-seat arena just minutes after Grande's concert ended.
