Mali army fires warning shots to halt Islamist advance BAMAKO (Reuters) - Malian soldiers fired warning shots on Tuesday at Islamist fighters pushing south towards their positions, military and diplomatic sources said, raising fears of the first clashes since militants seized Mali's north in April. The capture of the northern two thirds of the arid West African nation by a loose coalition of Islamist groups has sown fears among Western and regional powers that Mali could become a haven for radicals to plot international attacks. Peace talks between some of the northern rebel groups and the government are scheduled for Thursday in Ouagadougou, the capital of neighboring Burkina Faso, but growing military tensions threaten to derail them. Ansar Dine, one of the main rebel factions, was one of several groups pushing southwards toward the line dividing government-held territory from arid northern Mali. The group had announced it ended a ceasefire because of international plans to deploy an African-led force to drive radical al Qaeda-linked fighters from Mali's north. Ansar Dine is seen as more hard-line than the Tuareg MNLA but less radical than MUJWA, which includes more foreign fighters and is considered to have ties with al Qaeda. A military source said on Tuesday the Malian army fired heavy artillery during the night to persuade the Islamist fighters to halt their advance. "The army fired warning shots at several points along the line during the night, to dissuade them," said the source at the defense ministry in Bamako. The warning shots were confirmed by a Western diplomat. Sanda Ould Boumama, a spokesman for Ansar Dine, refused to comment on whether any fighting had taken place. Once an example of democracy and development in turbulent West Africa, Mali was plunged into crisis by a March 2012 coup which allowed Tuareg rebels to seize the country's north, demanding an independent homeland. Islamists who initially fought alongside them soon came to dominate the rebellion. There appears scant chance of a breakthrough in this week's talks. Ansar Dine has insisted it will not drop its demands for Islamic law and autonomy for northern Mali, while President Dioncounda Traore, installed after March's coup, has insisted he will not compromise over Mali's secular state and territorial integrity. Reporting by Tiemoko Diallo in Bamako, Bate Felix in Dakar and Joe Bavier in Abidjan; Writing by Daniel Flynn; Editing by Tom Pfeiffer