Geneva - Libya is facing "political impasse" and "hazardous military developments", the UN envoy to the North African country Martin Kobler warned on Tuesday, highlighting the impact of violence on civilians.
The country has been ravaged by unrest since the fall and death in 2011 of dictator Moamer Kadhafi and has also seen the jihadist Islamic State group establish a foothold.
A Government of National Accord supported by the United Nations and Western powers was established in the capital Tripoli in March, but has been unable to assert its authority in the face of a rival administration in the east of the country.
"Unfortunately, we are now facing a political impasse," Kobler told a meeting of the UN's Human Rights Council in Switzerland.
"At the same time, Libya is witnessing the unfolding of dangerous military developments," he said, citing the takeover of key oil facilities by the forces of controversial Marshal Khalifa Haftar who does not recognise the GNA.
He also cited the fighting between forces loyal to the GNA against IS in Sirte, "with nearly 600 killed and thousands injured".
"The risk of increased tensions in the capital should not be underestimated," the UN envoy added.
"The multiple armed conflicts raging in Libya continue to directly impact the lives of civilians," Kobler said, adding that between March 1 and August 31 the UN had "documented 287 civilian casualties, including 141 deaths and 146 injuries".
Among the victims were 30 children killed and 28 wounded.
He said that in Libya's second city Benghazi in the east, "more than 100 families are currently trapped in areas of fighting, facing constant bombing and shortages of food, medical care and electricity".
The economy has also been badly hit.
"The government is spending 93% of its total budget on subsidies and salaries, including those of members of armed groups that are not under the control of the government," Kobler said.
"Armed groups around the country continue to carry out grave human rights abuses with total impunity," he said, adding that this "must be addressed as a matter of urgency".
The UN envoy also highlighted "the horrific plight of migrants, refugees and asylum seekers" trying to reach Europe from Libya.
Many board rickety, makeshift vessels operated by people traffickers to head for Italy, but many also drown during the perilous journey.
Kobler said the UN was seeking an end to the arbitrary detention in Libya of migrants and the closure of a number of detention centres "where women are particularly exposed to abuses including sexual violence".