KARACHI , Pakistan ( CNN ) -- Police in Pakistan arrested lawyers holding a public protest to demand that the government immediately restore judges the previous president had ousted , Karachi 's police chief told CNN Thursday . Lawyers shout slogans Thursday in Karachi on the eve of a march to Islamabad . Among those detained were Muira Malik , former president of the Supreme Court Bar Association and leader of the Karachi lawyers movement , and retired high court justice Rasheed Razvi , police Chief Wasim Ahmed said . The lawyers were arrested under an order that outlaws public gatherings . The police chief also said authorities had credible information that there was a terror threat against the march and he had warned the lawyers before they started that it would be a public danger . Up to 500 lawyers in the Karachi group planned to join thousands of other demonstrators heading to the capital , Islamabad , as part of a four-day `` Long March . '' The demonstrators plan a massive sit-in at the parliament building Monday . `` Our movement is a peaceful movement , '' organizer Razvi , president of the Sindh High Court Bar Association , said before his arrest . `` When we protested the last time , there were hundreds of thousands of people and not one grass was broken , not one leaf was broken . '' The demonstrators began walking from the gates of the Sindh High Court , heading to a dozen buses that waited to ferry them to their next stop : the city of Hyderabad . `` The rule of baton and bullets can not last , '' the protesters chanted . They want President Asif Ali Zardari to live up to a promise to reinstate judges sacked by then-President Pervez Musharraf . Among the dismissed judges was the chief justice of the Supreme Court , Iftikhar Muhammad Chaudhry . After sweeping into power in parliamentary elections last year , Zardari 's Pakistan Peoples Party promised to reinstate the judges within 30 days of taking office . The deadline came and went . The government responded to the recent intensification of protests by banning political demonstrations in two of the country 's biggest provinces -- Punjab and Sindh . It also detained several hundred activists Wednesday . But the protesters said they will not be deterred . Their movement now , they said , is n't so much about reinstating Chaudhry as it is about restoring the office of the chief justice . `` We will start the long march from the province as we have promised the nation , '' Razvi said . The country 's largest opposition party , the Pakistan Muslim League-N ( PML-N ) , is backing the lawyers -- but for reasons of its own . Party head Nawaz Sharif accuses Zardari of being behind a February Supreme Court decision that bars Sharif from holding public office . The court also stripped Sharif 's brother , Shahbaz , of his post as chief minister of Punjab -- the Sharif party 's power center . Supporters of PML-N have responded by holding massive rallies , some of which have turned violent in recent days . CNN 's Thomas Evans and Zein Basravi contributed to this report .
NEW : Lawyers arrested at start of 'Long March ' protest to the capital , Islamabad . Comment: They want judges removed by previous president be restored to office . President Zardari 's party had vowed to reinstate judges after winning election .