BENGHAZI, Libya (AP) — The only functioning airport in Libya’s capital closed Wednesday after coming under attack, despite a tenuous truce that world powers have pushed warring parties to respect.

Authorities at Tripoli’s Mitiga airport said six Grad missiles crashed into the tarmac, prompting the airport to briefly suspend operations. When calm returned, flights resumed — only to be grounded yet again following fiery threats from eastern-based forces laying siege to the capital.

As the sole landing strip for the U.N.-backed government based in Tripoli, as well as its major military base, Mitiga is a strategic target for opposition forces led by Gen. Khalifa Hifter.

A spokesman for Hifter's forces acknowledged shooting down a Turkish-made drone over Mitiga. There were no reports of damage or casualties. Hifter's forces, known as the self-styled Libyan Arab Armed Forces, alleged the unmanned drone violated the cease-fire and tried to strike LAAF targets in the capital.

Turkey provides the embattled U.N.-backed administration with military support and, in a contentious move, recently deployed troops to help.

A pro-Hifter news outlet shared footage of dozens of people crowding around to inspect wreckage of the drone. One of its large shattered pieces bore the Libyan flag.

At a news conference, a spokesman for Hifter's forces, Ahmed al-Mosmari, said they were imposing a no-fly zone over Mitiga airbase and “any civilian or military aircraft that breaches the airspace will face a strong and immediate response." Striking a harsh tone, he warned that Hifter's forces would not hesitate to bomb a western militia stronghold at the airbase.

The airport, after having reopened just hours before, was abruptly shut down. Officials said all planes taking off Thursday would be diverted to a northwestern city.

The heightened tensions tested the resilience of a cease-fire brokered earlier this month by Russia and Turkey as diplomatic efforts to halt the civil war intensify. The two countries, supporting rival factions in Libya, have become central players in the conflict over recent months.

Although both Hifter's forces and the U.N.-backed government announced they would abide by the truce, intermittent clashes continue to rattle residents on the outskirts of Tripoli.

On Sunday, world powers with interests in oil-rich Libya held a peace summit in Berlin, where they pledged to halt foreign interference and honor a widely violated arms embargo.

The peace push followed a surge in Hifter’s offensive against Tripoli, which has threatened to plunge Libya into chaos rivaling the 2011 conflict that ousted and killed longtime dictator Moammar Gadhafi.

Basic questions about a concrete political process remain unresolved.

The foreign ministers of Libya’s neighboring countries are set to meet in Algeria on Thursday for discussions on “rapidly changing developments” following the Berlin conference, according to Egypt’s Foreign Ministry.

Hifter’s forces, which control the east and much of the south, receive support from the United Arab Emirates and Egypt, as well as France and Russia. The Tripoli-based government is backed by Turkey and to a lesser degree Qatar and Italy.