The closest rebel-held city to the Libyan capital has fallen to Muammar Gaddafi's forces.
And on another fighting front near the opposition-held east of the country, government forces trying to stop rebels advancing towards Tripoli pounded them with airstrikes and rockets.
The latest round of battles on opposite ends of Libya's Mediterranean coast once again revealed the weakness and disorganisation of both sides in the conflict.
Gaddafi's regime has been using its air power advantage more each day to check a rebel advance west toward Tripoli on the main road leading out of the opposition-controlled east.
The increasing use of planes underlines the vulnerability of the rebel forces as they attempt to march in open terrain and could prompt world powers to impose a no-fly zone over Libya to deny Gaddafi that edge.
In Zawiyah, 30 miles west of Tripoli, government forces and rebels who had been in control of the city fought for weeks with the power tipping back and forth between the two sides.
After the government brought overwhelming firepower in a counter-offensive that lasted all weekend, the city fell to Gaddafi's forces last night.
The government heavily shelled the city with tank artillery and mortars, according to one witness who said Gaddafi's tanks were roaming the city and firing randomly at homes.
He said electricity, phone and internet services were all cut. He managed to escape the city through surrounding farmlands and reach a point where mobile phone coverage was available. The recapture of Zawiya was confirmed by regime officials in Tripoli.
"The city is in ruins," he said. "Some buildings have been entirely destroyed and everyone on the street is shot on sight. There are many wounded but the hospitals are running out of supplies," he said. The offensive on Zawiya is thought to be spearheaded by an elite unit led and named after one of Gaddafi's sons, Khamis.
On a separate front in the east, Libyan planes launched at least five new airstrikes today near rebel positions in the oil port of Ras Lanouf.
Over the past few days, rebels moved out of their stronghold in the east, capturing with relative speed the oil ports of Brega and Ras Lanouf. But they were met with superior firepower and airstrikes when they tried to push westward and beat a fast retreat to Ras Lanouf over the past two days.
Government forces also pounded the rebels with rockets.
The rebels marching west seem to have reached a point of their campaign where they need to work out how to organise resupply lines and avoid becoming easy targets for planes. The extent of their westward reach is a checkpoint about six miles west of Ras Lanouf.
Today's airstrikes appeared designed to intimidate the rebels rather than kill them, but the anti-regime forces were not taking any chances and were spreading out deep inside the desert around the area in small groups.
In Benghazi, a spokesman for the newly created Interim Governing Council said a man who claimed to represent Gaddafi made contact with the council to discuss terms for Gaddafi to step down.
Mustafa Gheriani said the council could not be certain whether the man was acting on his own initiative or did in fact represent the Libyan leader.
"But our position is clear: No negotiations with the Gaddafi regime," he said.
However Western military intervention does not seem imminent - and the warnings may be an attempt to intimidate Gaddafi with words before deeds.
British and French officials said a no-fly zone resolution was being drawn up as a contingency and it has not been decided whether to put it before the UN Security Council, where Russia holds veto power and has rejected such a move.
Western officials have said a no-fly zone does not require a UN mandate, but they would prefer to have one.