The British government has increased its prison capacity to help tackle violent, week-long anti-immigrant riots that have prompted a growing number of countries to warn their citizens about the dangers of travelling in Britain.

Riots across a number of towns and cities have erupted following the murder of three girls in Southport, a seaside town in northern England, after false messaging on social media wrongly identified the killer as an Islamist migrant.

The justice department, which is being forced to release some prisoners early as it battles a jail overcrowding crisis, said nearly 600 prison places had been secured to accommodate those engaged in violence. About 400 people have been arrested so far.

“My message to anyone who chooses to take part in this violence and thuggery is simple: the police, courts and prisons stand ready and you will face the consequences of your appalling acts,” justice secretary Shabana Mahmood said.