MOGADISHU, July 19 (Reuters) - Explosions echoed in Somalia's Bakara market in the heaviest fighting in 15 days of non-stop violence, hours before crucial reconciliation talks were expected to resume on Thursday, residents said. Suspected insurgents fired rockets, mortars and grenades overnight at Somali forces patrolling the sprawling market before laying down machinegun fire for nearly an hour. Witnesses said a shop selling fuel was on fire, with others in the market. "The sky was lit by the explosions," grocery shop owner Mohamed Abdi told Reuters. "It was the heaviest attacks so far on the troops. The gunmen fired rockets, mortars and grenades at them. The market is tense. There is no news of casualties yet."