Italy’s Prime Minister Matteo Renzi (R) and Bernardino Leon, Head of United Nations Support Mission in Libya (UNSMIL), talk during a meeting at Chigi Palace in Rome March 11, 2015.

European powers and the United States welcomed renewed dialogue between Libya’s rival political factions, amid U.N.-mediated talks aimed at reaching an agreement to form a unity government in the strife-torn country.

In a joint statement, France, Germany, Italy, Spain, Britain and the United States urged the participants in the talks to “enter into the discussions constructively and in good faith in order to reach agreement on a national unity government and arrangements for a ceasefire as quickly as possible.”

“We call on the Libyan political leaderships to act responsibly and to make clear their support for the dialogue and call on them to exercise authority over military and militia leaders and ensure civilian oversight and control of their actions and disavow military actions not taken in that framework,” they added.

“We are deeply concerned about the growing threat from terrorist groups in Libya, including Da’esh, who have expanded their presence in Libya as a result of the absence of a strong, united, central government in the country,” the world powers said, using an Arabic acronym for the ISIS group.

“The United Nations-led process to establish a national unity government provides the best hope for Libyans to address this terrorist threat and to confront the violence and instability that impedes Libya’s political transition and development.”

Separately, Libya’s official government conducted air strikes on Saturday against airports and a military camp in the capital Tripoli, controlled by a rival government, and killed a senior commander loyal to that government, officials said.

The internationally recognized government said on Friday that it had launched a military offensive to “liberate” Tripoli, which a group called Libya Dawn seized in August, reinstating a previous parliament.

A Tripoli official said Salah Burki, a Libya Dawn leader, had been killed west of Tripoli, where a state news agency reported clashes between Libya Dawn and forces from Zintan allied to Thinni.

Details were unclear. Another official and some news websites said Burki had been killed in an air strike on a military camp in Tripoli.

Saqer al-Joroushi, an air force commander loyal to the eastern government, said earlier that his aircraft had bombed Mitiga airport in Tripoli and a camp used by Libya Dawn near another airport in the capital.

He said they had also attacked the airport in Zuwara, a town near the Tunisian border, west of Tripoli. An airport official said the runway had been hit but there were no casualties.

On Friday, U.N. Special Envoy Bernardino Leon said the military offensive threatened international efforts to reach agreement in the next few days on a unity government and lasting ceasefire.

Western leaders say the U.N.-brokered talks are the only way to end the chaos in Libya, where Islamist militants have also gained ground. Both sides have attacked each other with warplanes in the past few days.

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