SANAA – Yemen will free northern Shi'ite rebel prisoners within days under a truce to end a war that drew in Saudi Arabia last year, an official said on Thursday, while clashes with armed separatists erupted in the south. Separately, a US-born radical preacher, believed to be in hiding in southern Yemen where he has been targeted by air strikes, said jihad against the United States was a religious duty and told American Muslims to reconsider their loyalties. A move by the government to free more prisoners would be a significant step toward cementing a fragile truce to end a northern war that has raged on and off since 2004, but analysts believe the deal is unlikely to last as it does not address the insurgents' complaints of discrimination by Sanaa. The rebels had freed at least 170 government soldiers and tribal fighters on Wednesday, a day after Sanaa accused them of dragging their feet in implementing the slow-going truce deal to end the war, which has displaced 250,000 people. "The Ministry of Interior is reviewing lists of prisoners and they are expected to be released in the coming few days," a government official told Reuters.