LONDON (Reuters) -Thousands of demonstrators joined rallies across Britain on Saturday as part of a “national weekend of action” against a proposed new law that would give police extra powers to curb protests. Scuffles broke out in the evening between police and protesters at one gathering in central London. “The policing operation in central London has now moved to the enforcement stage and arrests are being made,” police said. “Officers continue to engage and we urge those who remain in the area to leave and return home.” The Police, Crime, Sentencing and Courts bill aims to toughen measures officers can take to disperse demonstrations, such as imposing time and noise limits, which campaigners and activists fear would be used to curb dissent. “Kill the bill” marches were held in dozens of towns and cities on Saturday, supported by big campaign groups such as climate change campaigners Extinction Rebellion and the Black Lives Matter movement. “(I’m here) to defend the rights of free speech, and the rights of organisations in our society,” said Jeremy Corbyn, the former leader of the opposition Labour Party who was among several thousand who demonstrated in central London. “These demonstrations, 50 of them today, will make a difference,” he told Reuters opposite the Houses of Parliament. Since the bill was brought before parliament last month, there have been sporadic protests. In the southwestern English city of Bristol, the demonstrations have turned violent with officers bombarded with missiles and police vehicles set on fire. Prime Minister Boris Johnson has criticised the “disgraceful attacks” on officers, but protesters have accused police of using heavy-handed tactics. A large crowd gathered again in Bristol on Saturday evening, although the rally there was peaceful. Days of protests by Extinction Rebellion, which paralysed parts of London in early 2019, fuelled calls from some politicians for the police to be given the tougher powers to prevent disruption. Demonstrations had not been permitted while a coronavirus lockdown was in place, but restrictions were eased this week, meaning the rallies could go ahead providing they were “COVID secure”. Some senior officers have said the “kill the bill” tag was deliberately provocative as “the bill” is a nickname in Britain for the police.