BANGUI—Rebels in the Central African Republic clashed with government forces on Thursday and threatened a renewed assault on the capital, after rejecting a last-ditch peace offer.       The Seleka rebel group seized two northern towns, hundreds of kilometers north of the capital Bangui, dismissing an offer from President Francois Bozize to agree to some of their demands as "too little, too late.’’The resumption of hostilities after more than two months of a ceasefire is a concern for France, which increased the number of troops in its former colony last year to protect citizens working there, many of them in the mining industry.CAR has rich deposits of gold, diamonds and uranium but it remains among the least developed countries in the world.Seleka says Bozize has not honored a January peace deal and had given him until Wednesday to do so.The attacks on Bouca and Batangafo happened hours after state TV announced two presidential decrees on Wednesday that failed to assuage rebel grievances. The decrees freed political prisoners, lifted curfews and banned roadblocks manned by pro-Bozize militia."We no longer trust Bozize’s promises. We are calling for him to resign, otherwise we will force him out,’’ Seleka spokesman Eric Massi said by telephone from France on Thursday.       A government official confirmed that rebel forces had first taken Bouca, a town with an airport some 300 km north of Bangui, before seizing Batangafo, 100 km to the north, later in the morning.Massi said Seleka’s forces had encountered light resistance from government troops in Bouca. The rebels captured three soldiers and two government army vehicles there, he said, and were unopposed in Batangafo.There were no immediate reports of other clashes but tensions ran high in Bangui over a possible return to fighting after rebels marched to the gates of the crumbling riverside capital in December.CAR’s current uprising is the latest in a long line of rebellions that have crippled the country. Conflicts in neighboring Chad, Sudan and Democratic Republic of Congo have also undermined peace efforts.The U.N. Security Council voiced strong concern about the situation on Wednesday and has called on all sides to abide by the January peace deal.Chad’s Foreign Minister Moussa Faki Mahamat said President Idriss Deby, in conjunction with his Congolese counterpart Denis Sassou-Nguesso, was seeking to organize a summit in Bangui to press for the peace accord to be implemented.As well as freeing political prisoners and removing checkpoints, the insurgents have refused to disarm before the departure of foreign peacekeeping troops, including some 400 South Africans.They also demand senior army posts for their military leaders as agreed under January’s power-sharing deal, which has already allowed rebels to enter the cabinet.In response to the rebel demands, Clayson Monyela, a spokesman for South Africa’s foreign ministry, said: "The troops are staying. They aren’t going anywhere.’’French nuclear energy group Areva has rights to CAR’s Bakouma uranium deposit.