The UN Security Council also called on the warring parties in Libya's capital Tripoli to rapidly return to UN-mediated political talks.
The UN Security Council called Friday for a ceasefire in Libya as the death toll from a three-month offensive on Tripoli reached 1,000 including scores killed in an air strike that hit a detention center for migrants.
The council condemned the attack late Tuesday on the Tajoura detention camp east of Tripoli and "stressed the need for all parties to urgently de-escalate the situation and to commit to a ceasefire," said a joint statement.
Meanwhile, UN High Commissioner for Refugees has called for an independent investigation into the strikes.
Libyan commander Khalifa Haftar, whose forces hold eastern Libya and much of the country's south, launched an offensive in early April to wrestle the capital from forces loyal to the UN-recognized Government of National Accord (GNA).
Air strikes and ground fighting have since left nearly 1,000 people dead and some 5,000 wounded, the UN's World Health Organization said.
The fighting has forced more than 100,000 people to flee their homes and threaten to plunge Libya into deeper conflict.
Among the dead are 53 migrants killed Tuesday night in an air raid on a detention center in the Tripoli suburb of Tajoura, held by the GNA, which accused Haftar's forces of carrying out the strike.
TRT World's correspondent Frank Ucciardo brings more from New York.
A Geneva-based spokesman for the International Organization for Migration said six children were among the migrants killed.
Joel Millman said that 350 migrants, including 20 women and four children, were still detained at the center, one of five air hangars hit in the raid.
World powers have been divided over how to respond to Haftar's offensive, with the United States and Russia refusing to condemn the Libyan strongman.
The British-drafted council statement condemned the attack on the migrant camp, called for a return to political talks and for full respect of the arms embargo on Libya.
It followed a closed-door council meeting on Wednesday during which US diplomats said they needed more time to consult with Washington on the proposed text.
The United Nations has called for an independent investigation to determine who was responsible for the strike on the center, which housed some 600 migrants, mainly from African countries.
TRT World's Philip Owira has more.
UN shared coordinates
UN agencies and humanitarian groups have repeatedly voiced concern over the plight of thousands of migrants and refugees held in detention centers near combat zones in the capital.
UN Secretary-General Antonio Guterres has expressed outrage over the attack and said the United Nations had shared the coordinates of the detention center with the warring sides to protect the civilians.
The carnage in Tajoura was "a tragedy that should have never happened", said Charlie Yaxley, spokesman for the UN's refugee agency.
Libya has become a major conduit for migrants seeking to reach Europe and remains prey to numerous militias vying for control of the country's oil wealth.
Rights groups say migrants face horrifying abuses in Libya, and their plight has worsened since Haftar launched the offensive against Tripoli.
According to the UN, some 5,700 refugees and migrants are being held in detention centers in Libya, 3,300 of which are vulnerable to fighting in and around Tripoli.
An initial lightning assault in early April saw Haftar's self-styled Libyan National Army steam towards the capital. But they have since been bogged down on its southern outskirts, where frontlines have been frozen for months.
The GNA forces launched a surprise counter-attack late last month, seizing the strategic town of Gharyan, the main supply base for Haftar's offensive.
After the setback, Haftar's forces threatened to intensify strikes against their rivals.
Both sides have launched daily air raids throughout the fighting and each lost several planes.
Troops loyal to Haftar said late Thursday they had downed a GNA jet near the town of Tarhuna, used by the LNA as a rear base some 80 kilometres southeast of Tripoli.
A GNA spokesman said they had lost contact with the L39 Albatros, which had been on a combat mission south of the capital, without providing further details.
The rival camps have remained convinced that with the help of their backers, they can win the battle.