Fears of a civil war and a humanitarian crisis grew in Libya as forces loyal to Muammar Gaddafi escalated attacks on rebel-held cities in a bid to recapture control, causing dozens of deaths and mass exodus of people.

Unlike in Tunisia and Egypt, the regime in Libya is not showing any sign of folding up without fighting to the last, worsening a civil war-like situation and confirming fears that the oil-rich North African nation is heading towards bitter, long struggle.

Gaddafi's forces intensified the battle to win control of the oil port of Ras Lanuf on Monday, flushing out hapless residents in droves. CNN said there were air strikes near the town and that rebel soldiers fired anti-aircraft guns.

The official army also recaptured control of the town of Bin Jawad, Reuters reported. Earlier, the rebel army lost some momentum in its march towards Tripoli, a stronghold of the 41-year regime.

For a few days the rebels were making gains, but overnight it would appear that pro-Gaddafi forces took some ground, Al Jazeera reported on Monday.

The mood was somber in the rebel citadel of Benghazi, as Gaddafi's forces made advances in flashpoints elsewhere in the country.

With helicopter gunships, fighter planes and tanks, Gaddafi loyalists have pounded opposition fighters with artillery, rockets and gunfire in several cities, including Bin Jawad, Tobruk, Ras Lanuf and Misurata, Al Jazeera reported.

Reuters quoted a military analyst as saying that the official forces have gained some ground of late. It's clear the government feels a sense of momentum on its side, the agency quoted Shashank Joshi, an associate fellow at Britain's Royal United Services Institute, as saying.

Reports have said the United Nations and the European Union are sending fact-finding missions to Libya to assess the situation in light of the unfolding humanitarian crisis.

The Secretary-General is deeply concerned about the fighting in western Libya, which is claiming large numbers of lives and threatens even more carnage in the days ahead, a UN statement said.