More than a dozen people were killed and more than 1,200 wounded in riots across England and Wales on Friday when rival groups clashed in towns in south London and in Manchester, the capital.

Authorities are investigating a possible second wave of violence in the capital, with witnesses reporting scenes of chaos, with police officers in riot gear using tear gas, batons and water cannons to disperse crowds.

Some in the crowd were seen being led away in stretchers by police officers, while others were pushed from a car onto the pavement.

Several people were arrested, and police said at least two were injured in clashes.

The capital saw dozens of riots in 2016, when crowds descended on Parliament Square and other public spaces in a bid to protest against the government’s controversial austerity measures.

In 2016, a protester died after he was punched in the head by an officer during an anti-austerity rally in central London.

In 2017, police responded to violent protests after rioters set off a fire at an anti-“Brexit” rally in the city.

The unrest was sparked by a plan by the British government to increase the number of seats for the House of Lords, the country’s upper house, from nine to 14 seats.

The plan has sparked a wave of protests in the UK, and the United States, that have led to the resignation of the prime minister and a wave in resignations of other top government officials.