Rival militias are locked in battle at Libya's main international airport, with reports of at least four people killed in the fighting.

Clashes resumed at Tripoli airport on Sunday, July 20, after attempts at a ceasefire failed. Missiles, rockets and tanks were said to be used, according to BBC News.

The fighting began last week, damaging planes and forcing the airport to shut.

Libya has been gripped by instability since the 2011 uprising, with swathes of the country controlled by militias. Successive governments have struggled to disarm the rival groups.

Fighters from the city of Zintan are fighting Islamist-led militias, including many fighters from Misrata, for control of the airport.

At least two of those killed on Sunday were civilians, security officials said.

"The airport was attacked this morning with mortar rounds, rockets and tank fire," Al-Jilani al-Dahesh, an airport security official, told AFP.

The fighting was described as the most intense since clashes erupted at the airport on July 12.

A spokesman for the district, Mohammed Abdulrahman, said residents were caught up in the fighting. "The shells are landing on us from all warring militias," he told Reuters.

Clashes were also reported at main road leading to the airport.

In a statement on its Facebook page, the European Union mission in Libya said it was "concerned about the protracted conflict over Tripoli International Airport", adding: "The only option is a political solution and a peaceful democratic process."