UN chief Antonio Guterres expressed deep concern Thursday over the risk of confrontation in Libya after forces loyal to a controversial strongman announced they were preparing to advance on Tripoli.

The African Union will host a "reconciliation" conference in July aimed at uniting Libya's political rivals, AU commission chief Moussa Faki said late Saturday.

The head of Libya's internationally recognised government and a military strongman who backs a rival administration in the country's east have met and agreed to hold elections, the United Nations said Thursday.

Armed men have murdered a security official in southern Libya, the U.N.-backed government said Thursday, a day after forces opposed to it said they had entered his town.

Militiamen have kidnapped a group of Tunisian workers near the Libyan capital Tripoli, demanding Tunis release a comrade, the foreign ministry and a rights activist said.

The US carried out an air strike against Islamist group Al-Qaeda in southern Libya on Wednesday night, Tripoli's UN-backed Government of National Accord said.

A military push in southern Libya which strongman Khalifa Haftar says is aimed at rooting out "terrorists" and foreign fighters has sparked backlash from an ethnic minority and the UN-backed government. 

French warplanes on Sunday carried out air strikes to halt an armed group that entered northern Chad from Libya in a column of 40 pickups, the French military said, adding it acted at Chad's request.

Civilian rescue vessel Sea Watch 3, which was detained in Sicily on Friday, is the latest in a long list of such ships that have been forced or have chosen to stop their work.

Currently only the Libyan coastguard is able to save those migrants floundering in their attempts to reach Europe across the central Mediterranean. 

Libyan army spokesman Ahmed al-Mesmari denounced the attack on his country’s flag in Beirut last week when AMAL Movement supporters removed Libyan flags and replaced them with the Movement’s flag, the Saudi Okaz newspaper reported on Tuesday.