At least 32 people were injured, according to reports from Tripoli hospitals, on the beach that runs alongside a coastal road into central Tripoli from the airport. The beach is popular with families trying to escape the city heat on summer evenings.

Photos posted on social media showed plastic furniture strewn on the sand under strings of outdoor lights.

Fighting started again early on Wednesday, local media said.

"The casualties are the result of clashes on Tuesday between a security force and outlaws who fired a shell that fell on a beach in front of Mitiga airport," Abdulsalam Ashour, a deputy interior minister in Libya's U.N.-backed government, told Libya Al-Ahrar TV channel.

Flights restarted at Mitiga after being suspended for several hours.

Some reports said the shell was fired in a revenge attack against members of one of the capital's many armed factions.

Tripoli is home to a patchwork of armed groups, some of which share control of Mitiga and the surrounding area. They occasionally clash over the control of smuggling businesses and in other local disputes.