Updated at 3:08 p.m. ET
TOBRUK, Libya - Muammar Qaddafi's forces bombarded two key rebel-held cities on Monday, witnesses said, attempting to seize back the country's east by the air even as rebels say they kept control of the streets in the region that holds most of the country's oil wealth.
Libya's upheaval has turned into a two-front conflict along the country's Mediterranean coast, where the majority of the population lives. Qaddafi appears to have somewhat of an upper hand. But his forces don't seem strong enough to overwhelm the rebels setting the stage for a grinding conflict as the West debated Monday whether to intervene, mulling the imposition of a no-fly zone that the rebels have been pleading for.
Ajdabiya and Brega are key crossroads for rebel supply lines, a main weakness. To get ammunition, reinforcements and arms to the front, they must drive along open desert highways, exposed to airstrikes. Qaddafi warplanes struck at least three targets Monday morning in Ajdabiya, missing a weapons storage site but hitting rebel fighters at a checkpoint in an attempt to stop supplies, rebels said.
Said Ali Bouhilfaya, an engineer in Ajdabiya, said there were renewed bombings Monday evening.
"It is a war of annihilation," Bouhilfaya said. "Mr. Qaddafi wants to stay in power even if he rules over graves."
Another resident in Ajdabiya said he heard a bombardment, but was uncertain whether it was an airstrike.
A rebel spokesman said a government plane dropped pamphlets over Ajdabiya earlier Monday, asking residents to eject anti-Qaddafi forces.
"Cut off their water and their food!" the pamphlets said, according to spokesman Abdul-Bari Zwei.
Qaddafi forces are trying to push back the long stretch of territory controlled by rebels nearly the entire eastern half of the country, which also has most of Libya's oil.
Government troops have scored victories using overpowering bombardments with artillery, tanks, warplanes and warships. Such an assault drove rebel fighters out of the oil port of Ras Lanouf several days ago.
But the regime offensive appears to be hampered by a lack of manpower: They can drive out rebels with barrages, but not necessarily hold the territory. After fleeing the bombardment Sunday, the rebels then pushed back into Brega in the evening and claimed to have captured dozens of fighters from Qaddafi's elite Khamis Brigade.
On Monday, about 2,000 rebel fighters mainly members of a special commando unit that defected to the opposition held Brega's residential district, while pro-Qaddafi troops controlled the industrial oil facilities some distance away, said Zwei. Rebel fighters were searching the residential area for any remaining Qaddafi troops.
Libyan state TV showed some images Monday from Brega port, claiming that it was in government control and at peace. The announcer urged Russia, China and India to invest in Libya's oil sector.
For the past week, the two sides have been battling for control over the two oil ports Brega and Ras Lanouf. But even if government troops take Brega as well, they may face even tougher resistance if they try to move further east, on the heavily populated cities that the opposition holds. Ajdabiya, 480 miles southeast of Tripoli, is the first of those cities.
Western Libya remains Qaddafi's stronghold, centered on Tripoli where his militiamen have crushed any attempts at an uprising. But since early on in the revolt, which began Feb. 15, several cities in the west fell into rebel hands. Regime forces on Friday took back the most crucial of those cities, Zawiya, which lies on the capital's doorstep, after a reportedly bloody and destructive week-long siege.
On Monday, pro-Qaddafi forces launched an attempt to take another, nearby town, Zwara, 70 miles west of Tripoli, close to the Tunisian border.
Government troops surrounded the town of 45,000 and bombarded it with tanks and artillery for hours starting in the morning, several residents said. At least four rebel fighters were killed in the barrage, said one resident, speaking on condition of anonymity for fear of retribution against him. The sound of gunfire could be heard over the telephone as he spoke.
One fighter, Shukri Nael, said he was among rebels who fended off an assault at a rebel checkpoint at one of the entrances to the city.
"I don't care how far the Qaddafi forces went east or how many cities they take back this is a chance for me to die for this country and become a martyr," he said.
On Sunday, regime forces began shelling the most significant rebel-held city in the west Misrata, Libya's third largest city, 125 miles southeast of Tripoli.
Troops on the city's outskirts and on ships off shore had sealed the city, cutting off water pipes to many of its neighborhoods and preventing water tankers from reaching the residents, said a local doctor and other residents. Residents were conserving existing water and food supplies, he said.
Opposition fighters were building sandbag fortifications and other defenses in anticipation that Qaddafi troops, positioned at an air base and military college about six miles from the city could launch an assault.
On Monday morning, a barrage of shelling slammed into houses on the edge of the city, said one resident. But by the afternoon the guns fell silent.
"There are divisions inside the (pro-Qaddafi) militia," said one rebel fighter, citing reports from fellow fighters closest to the government troops. "Some of the forces don't want to enter the town and attack civilians. Others want to attack the city, Others want to join the rebels. Those wanting to attack the town are attacking the refuseniks."
The report of divisions could not be independently confirmed.
The opposition has been pleading with the West to impose a no-fly zone to help balance the scales with Qaddafi's forces. But for weeks, Western nations have been divided and hesitant on the move.
France and Britain were making an accelerated push Monday for a no-fly zone as U.S. Secretary of State Hillary Clinton and other top diplomats from the G-8 group of prominent world economies were gathering in Paris for a previously planned foreign ministers meeting.
France, which has angered some allies by offering diplomatic recognition to Libya's opposition, said it is urgent to act against "barbarity" by Qaddafi's forces.
In Britain, Foreign Secretary William Hague said Libyans will face a "nightmare" if Qaddafi regains control, insisting that the world is "reaching a point of decision" on whether foreign forces will impose a no-fly zone.
Other countries, including the United States, have been more cautious.