At least two people have been killed in clashes between rival militias in the Libyan capital of Tripoli.

The fighting on Wednesday violated a UN-brokered ceasefire which was signed four months ago.

"The clashes resulted in two killed and 17 wounded from both civilians and fighters," Tripoli health department official Malik Marsit told Reuters news agency.

The groups involved in the clashes are known as the Seventh Brigade, or Kaniyat, and a collection of factions called Tripoli Protection Force.

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The Seventh Brigade and some allied groups triggered the August fighting in a bid to challenge the dominance of four "super militias", including the Tripoli Protection Force, in the streets of the capital.

The UN mission in Libya condemned the renewed fighting in an official statement on Twitter, adding that it "warns parties against any breach of the ceasefire agreement, compromising stability in the capital & endangering lives of civilians & their properties".

"The mission stresses that any party initiating a confrontation will be held fully responsible," it added.

UNSMIL strongly condemns the recent military mobilisation of forces in southern #Tripoli & warns parties against any breach of the ceasefire agreement, compromising stability in the capital & endangering lives of civilians & their properties. https://t.co/cUnkY2wctv pic.twitter.com/QFJg6mizUl — UNSMIL (@UNSMILibya) January 16, 2019

The internationally recognised government in Tripoli, backed by the United Nations, has been working on a new security plan since the ceasefire deal but achieved little as Libya, long a major oil producer, lacks a national police force or army.

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During the clashes in September, the International Committee of the Red Cross (ICRC) described the situation in the north African country as "desperate", with the fighting, collapsed economy and destruction of infrastructure leaving hundreds of thousands of people "increasingly vulnerable".

"Seven years of war in Libya has driven over 500,000 people to flee their homes," the ICRC said in a tweet.

"For Libyans trying to return home, there's not always much to return to. Houses, schools are often destroyed completely."

The group also cited the sabotaging of health facilities, water and electricity supplies, as well as the dangers of unexploded remnants.