More than 1 700 families have been displaced by fighting in Libya's war-ravaged capital over the last 48 hours, the United Nations (UN) has said, as clashes between rival groups intensify.

The UN Office for the Coordination of Humanitarian Affairs (UNOCHA)said on Monday that at least 1 700 families had sought "safer areas" since Sunday, bringing the total number of families driven from their homes since August 26 to 5 000.

"Many are afraid to leave their homes because of looting by armed groups or criminal elements," UNOCHA said in a statement.

"As the fighting escalates, the number of civilians affected by violence is bound to increase."

After nearly a month of sporadic clashes, the total number of civilian killed stood at 115, with at least 560 people wounded, it said.

Eleven people had been killed, most of them civilians, since Saturday, it added.

The capital has been gripped by fighting since late August when the Seventh Brigade, an armed group based in Tarhouna, 65km southeast of the capital, and an allied militia from the town of Misrata, launched a surprise offensive against against the Tripoli Revolutionaries' Brigades and the Nawasi, two of the capital's biggest militias.

The militias from Tarhouna and Misrata say they are fighting to rid the capital of militias that are "blackmailing state institutions", while the Tripoli-based militias say they are trying to expel "criminals and outsiders".

Both sides technically operate under Libya's internationally-recognised Government of National Accord.

'Situation is desperate'

According to witnesses, heavy weapons, including artillery, have been used in the fighting, with residential areas, mainly in the southern outskirts, hit by what seems to be random shelling.

The UN helped broker a ceasefire on September 4, but that has been breached repeatedly by both sides.

Libya has been gripped by tribal and factional fighting nearly seven years after the overthrow of former leader  Muammar Gaddafi.

The existence of two rival legislatures - the internationally recognised Government of National Accord (GNA) and the House of Representatives (HOR) based in eastern city of Tobruk - each with its own central bank and national oil company - highlights another challenge in the country's plight to enact the necessary reforms and, ultimately, hold elections.

The International Committee of the Red Cross (ICRC) has 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".