Rebels in Libya said five opposition fighters were killed in a NATO air strike Thursday near Brega, and in Misrata a government artillery barrage left five dead and 25 wounded.

NATO said the situation in Brega was “unclear and fluid,” but officials are investigating the rebel claim of friendly fire casualties. If the reports are correct, it will be the second such incident in less than a week.

The fighting around Brega has been a week-long tug-of-war with neither side gaining an advantage. U.S. commander General Carter Ham, speaking in Washington, indicated the fighting may be reaching stalemate. Neither side can gain the upper hand despite enforcement of the no-fly zone and NATO air support.

The port facilities in Misrata, where vital supplies are being delivered to the city, were temporarily closed following the bombardment Wednesday. Concern for the civilians grows daily as they endure the attacks and shortages of basic supplies.