Fighters from the two main rebel groups occupying northern Mali exchanged fire near the town of Timbuktu on Wednesday, officials and local residents said, highlighting tensions between Islamists and separatists vying for control of the desert zone. It was not immediately clear what the toll was from the shooting, but the clash marks a ratcheting up of tensions between the separatist MNLA and Islamist Ansar Dine rebels who, just weeks ago, said they would merge to run an independent Islamic desert state. The African Union has called on the United Nations Security Council to give it a mandate to dispatch a force to Mali to help restore authority in the north, which experts warn has become a safe haven for criminals and extremists, including al Qaeda. A local member of parliament and other sources said the clash took place just outside Timbuktu, on the road to Goundam, to the southwest, when Ansar Dine fighters tried to stop MNLA gunmen travelling in a vehicle. \"There was an exchange of fire and the wounded were taken to hospital,\" said El Hadj Baba Haidara, member of parliament for Timbuktu, said by telephone. \"There are reports of one dead on the MNLA side but it is not clear,\" he added. MNLA spokesman Attaye Ag Mohamed blamed the shoot-out on al Qaeda, but said the fighting was short-lived. \"Al Qaeda elements blocked our vehicles from entering the town. It was just a small incident,\" he said, without giving details on dead or wounded. An Ansar Dine spokesman was not available. Mohamed Dicko, a town resident, said Ansar Dine gunmen were in vehicles racing out of town in the direction of the clash. Another resident, who asked not to be named, said the clash followed several days of efforts by Ansar Dine fighters to disarm the MNLA, whose positions there are mainly limited to the town\'s airport. \"The MNLA are not getting on with Ansar Dine ... It has been tense for a week in Timbuktu,\" he said. The two groups battled Malian government forces for weeks before a March 22 coup led to the army\'s resistance crumbling and the fall of the three main northern towns in as many days by early April. After weeks of awkward joint occupation of the Kidal, Gao and Timbuktu, the MNLA and Ansar Dine announced a merger in late May. But the deal was never finalised due to differences over the application of Islamic law, sharia. Meanwhile, with Mali\'s politicians and military still bickering over control of the capital, African and Western powers have warned of the growing threat of the security void, and many say foreign intervention is needed to retake control of the zone, which is the size of France.