The U.N. special envoy to Libya has condemned airstrikes against the Tripoli airport as one of the delegations to ongoing peace talks was attempting to leave.

Bernardino Leon told reporters Wednesday at the start of the latest round of Libyan peace talks in Morocco that it was unacceptable and there should be an explanation by those behind the attack.

"We have never seen airstrikes in the moment in which one of the delegations is taking off on its way to the talks," he said.

Representatives from Libya's rival governments have been meeting for a month in Morocco to discuss a U.N. proposal for a unity government to end the fighting.

Gen. Khalifa Hifter, commander of the anti-Tripoli forces, possesses an air force and has condemned the talks as a dialogue with "extremists."