British Prime Minister Keir Starmer said violent protesters who had targeted Muslim communities would swiftly face the "full force of the law" as he sought to quell days of anti-immigration rioting. The fatal stabbing of three young girls in the northwest English town of Southport last week has been seized on by anti-immigrant and anti-Muslim groups, with disinformation spread online and amplified by high-profile far-right figures to spark disorder in towns and cities. "Whatever the apparent motivation, this is not protest, it is pure violence and we will not tolerate attacks on mosques or our Muslim communities," Starmer said on Monday after an emergency meeting with police and prison chiefs. "The full force of law will be visited on all those who are identified as having taken part." Police chiefs said they had arrested 378 people since the start of the unrest and warned of "lengthy prison terms" for those found guilty of violent disorder.