London, May 29 (IANS/DPA): Three police officers were injured, and 40 people have been arrested during a protest in London.

One officer was left with a serious facial injury after she was hit by a bottle thrown from the crowd, while two officers had minor injuries on Tuesday night.

Metropolitan Police said the suspect who threw the bottle has not been identified, but police are investigating.

A protest organised by a coalition of groups, including the Palestine Solidarity Group, began at around 6 pm (1700 GMT) and was required to end at 8 p.m. on Tuesday night, police said.

The majority of the crowd, which was between 8,000 and 10,000 people, left Whitehall without incident.

A group of around 500 people remained, and police began making several arrests for failing to comply.

Police said some of the crowd resisted arrest, which required police to use force to remove those who had been arrested before the protest broke away with the crowd marching to Bridge Street, outside Westminster Station, where police put up cordons to detain the group.

A police statement said they went into the crowd shortly before 10 p.m. to arrest those suspected of leading the breakaway protest, with 40 people arrested for offences including breaking the Public Order Act, obstruction of a highway and assaults on emergency workers.

Around 2 a.m. on Wednesday, police said all protesters had left the area, and Bridge Street had been reopened.