Rebel Tuareg fighters of the National Movement for the Liberation of Azawad (MNLA) clashed with Islamist fighters from the Ansar Dine groups overnight in northern Mali, witnesses said Friday. \"Fighters of the MNLA and those of Ansar Dine clashed overnight Thursday to Friday on the outskirts of Kidal,\" an official from the rebel-held town told AFP by phone. A resident said it had involved a heavy exchange of fire.