N'DJAMENA - Chad's government accused the United Nations' peacekeeping mission in Mali on Friday of failing to relieve its contingent in the country's volatile north and neglecting to support it, a day after five Chadian soldiers were killed by a roadside bomb.The mission, known as MINUSMA, was deployed last year after a French-led military intervention drove out al-Qaida-linked Islamist fighters, who had seized the north a year earlier.Pockets of insurgents remain, however, and the Kidal region has seen a steep rise in attacks and landmine explosions targeting both U.N. troops and civilians.Five Chadian soldiers were killed and three others were injured on Thursday when their vehicle hit an explosive device between the desert towns of Aguelhok and Tessalit. All of the 10 peacekeepers killed in Mali so far this month have been Chadian."Since their deployment, Chadian forces have remained stationed in the north, without being relieved," government spokesman Hassan Sylla said in a statement. "The government cannot accept that the Chadian contingent serve as a shield for the other contingents positioned further back."He said Chad's force in Mali was experiencing enormous difficulties with logistics, mobility and ensuring its troops were properly fed.The government said it would give MINUSMA one week to relieve its troops and give them the necessary support, although it did not say what it would do if its demands were not met.