MEDAN: Indonesia's underground union leader, who has vowed to risk detention and torture to further the workers' cause, was arrested yesterday. A relative of Muchtar Pakpahan said five policemen arrived at Mr Pakpahan's home early yesterday with a warrant for his arrest. They said he would be taken to Medan, in Sumatra, and face questioning over riots that followed workers' protests last April. ''This is a war for human rights and a war we intend to win,'' he told the Sunday Morning Post recently, while in hiding after other leaders of the outlawed Serikat Buruh Sejahtera Indonesia were arrested. The diminutive ex-lawyer from Sumatra then vowed to bring down the Indonesian Government in order to improve conditions for workers. Worker rights and factory conditions have been at the centre of continuing talks between the United States and Indonesia on preferential trade policies. The US this month again postponed a decision on whether to grant the tariffs pending further review of Indonesian labour policies. Mr Pakpahan has been questioned twice by Medan police in relation to a week-long mass workers' demonstration in mid-April in the city. The protests were followed by race riots in which at least one ethnic Chinese businessman died and in which scores of factories, cars and homes were damaged. Sejahtera official, David Pela, said Mr Pakpahan's arrest warrant cited two allegations, one of publicly inciting people to crime and violence against the authorities and another of holding a street rally without a police permit. The first charge carries a maximum of six months in jail while the second carries a sentence of up to two weeks. Mr Pela said a summons had been issued for August 11 but that an arrest warrant could only be issued after two summonses had been ignored. Authorities have blamed Sejahtera for the unrest that triggered the race riots. Mr Pakpahan has admitted the union was behind the initial workers' protest but denies planning the ensuing violence. Sejahtera was set up in July 1992 as a splinter group from the country's first independent trade union, the Setiakawan (Solidarity) Free Trade Union, which was set up in 1990.