UNITED NATIONS (AP) — The United Nations said Wednesday its regular flights have not been granted permission to land in Libya by the self-styled Libyan Arab Armed Forces led by Gen. Khalifa Hifter.

U.N. spokesman Stephane Dujarric said the U.N. mission in Libya was concerned that its regular flights into Tripoli, which transport U.N. staff to and from the war-torn country, have been prevented from landing on several occasions in the past weeks.

Dujarric said preventing U.N. flights from traveling in and out of Libya “will severely hinder our humanitarian and good offices efforts” at a time when the United Nations is trying to get the warring parties to negotiate a peace agreement and “provide much-needed humanitarian assistance to the most vulnerable conflict-affected civilians.”

Libya has been in turmoil since 2011, when a civil war toppled longtime dictator Moammar Gadhafi who was later killed.

A weak U.N.-recognized administration that holds the capital Tripoli and parts of the country’s west is backed by Turkey, which recently sent thousands of soldiers to Libya, and to a lesser degree Qatar and Italy.

On the other side of the conflict is a rival government in the east that supports Hifter, whose forces launched a surprise offensive to capture the capital last April and are backed by the United Arab Emirates and Egypt as well as France and Russia.

Dujarric was asked why the U.N. needs permission from Hifter’s forces in the east for its planes to land in Tripoli.

“I think we just want to make sure we have all the necessary clearances,” he said. “It goes without saying that you want to make sure that all the passengers on the plane are safe. Flight clearance is pretty basic. We’re not landing fighter planes, we’re landing passenger planes.”