More fighting broke out between rival armed groups in Tripoli on Wednesday night despite a truce announced hours earlier, prompting a protest demanding the resignation of the government.
Violent clashes began on Monday, which ended three years of relative calm in Libya's capital, following the killing of prominent militia leade, Abdel Ghani Al Kikli, also known as Gheniwa.
Clashes flared between the Radaa force and the 444 Brigade in key areas of the city, including the port. Fighting had eased by the early hours of Thursday, according to television reports and residents who spoke to AFP, with some bakeries opening but schools remaining shut.
No casualty figures were released but the Libyan Red Crescent said it had recovered a dead body from a major street in Tripoli.
Protests broke out with hundreds of angry demonstrators flocking to Algiers Square in the heart of the capital, urging the so-called national unity government to step down.
Demonstrations were seen in areas such as Souq Al Juma and Al Hadaba, with people holding signs demanding the resignation of the government, the withdrawal of all armed groups from residential areas and that state institutions are overseen by the proper authorities.
The protesters denounced the culture of impunity and the absence of a political vision to end the division of the country, which remains split between a UN-recognised government in Tripoli, led by Prime Minister Abdul Hamid Dbeibah, and a rival administration in the east.
The 444 Brigade controls parts of southern Tripoli and is aligned with Mr Dbeibah. Radaa controls areas of the capital's east and holds several key state facilities.
The violence extended to southern and western Tripoli, as Radaa brought in reinforcements to fight the 444 Brigade, an Interior Ministry source said.
The embassies of Germany, France, the US, Britain and Italy on Wednesday evening expressed "their deep concern about the recent violence in Tripoli", urging the "authorities to take all measures to protect civilians" in a statement.
The UN mission in Libya said it was "deeply alarmed by escalating violence in densely populated neighbourhoods of Tripoli".
In a statement, it called for "an immediate, unconditional ceasefire in all areas, allowing safe corridors for the evacuation of civilians trapped in intense conflict zones".
