Thousands of Tamils in Britain joined a vigil in Parliament Square on Tuesday to protest against the Sri Lankan government’s military offensive.
Human rights organisations have reported massive civilian casualties as a result of recent government shelling.
Demonstrators blocked Westminster Bridge before police pushed them back.
The protests demanded an immediate end to the Sri Lankan government’s bombardment of areas once under the control of the separatist Tamil Tiger movement.
Police arrested several protesters in London under anti-terror laws for waving flags of organisations banned by the British government.