BENGHAZI, Libya — Moammar Gadhafi's forces swept rebel fighters out of a key oil town and into the desert Sunday with searing waves of artillery fire and airstrikes, extending their rapid advance on the poorly equipped and loosely organized fighters.

The United States, meanwhile, was sending its top diplomat to make contact with Gadhafi opponents in Paris, as it and other world powers considered trying to ground his air force with a no-fly zone that carries many of its own risks.

Rebel officials in their stronghold of Benghazi told The Associated Press that Brega, the site of a major oil terminal, came under heavy shelling Sunday. Libyan state television and a military spokesman said government troops had retaken the town, and several rebel fighters heeding orders to fall back under the heavy bombardment said the town slipped out of their control.

The loss of Brega is the latest in a series of setbacks for opposition forces who just a week ago held the entire eastern half of the country and were charging toward the capital, Tripoli. Gadhafi's troops have reversed many of those early gains, bearing down on the rebels with superior firepower from the air.

The rebels are fighting to oust Gadhafi from power after more than 41 years, inspired by protesters who toppled authoritarian rulers in neighboring Tunisia and Egypt. However, the Libyan uprising has already proved much more violent, and could be the start of a drawn out and bloody civil war.

Gadhafi's forces pushed the front line miles deeper into rebel territory Saturday to just 25 miles (40 kilometers) outside Brega. Sunday's state TV report declared the city has been "cleansed from armed gangs."

While those military forces still loyal to him appeared to have seized back some momentum, Gadhafi is becoming more internationally isolated. U.S. Secretary of State Hillary Rodham Clinton was set to leave Sunday for a trip to Europe and the Middle East to establish the Obama administration's highest-level contacts with the Libyan opposition.

She plans to see foes of Gadhafi in Paris on Monday to assess their capabilities and intentions.

The Arab League has also shunned the Libyan leader and asked the U.N. Security Council Saturday to impose a no-fly zone. In surprisingly aggressive language, the 22-member bloc said the Libyan government had "lost its sovereignty" and asked the United Nations to "shoulder its responsibility" and impose the restriction.

The rebels have called for a no-fly zone as well, saying they are no match for the Gadhafi regime's fighter jets.

The U.S. and many allies have expressed deep reservations about the effectiveness of a no-fly zone, and the possibility it could drag them into another messy conflict in the Muslim world. Western diplomats have said Arab and African approval was necessary before the Security Council voted on imposing a no-fly zone, which would be imposed by NATO nations to protect civilians from air attack by Gadhafi's forces.

A military spokesman told reporters in the capital that Brega was under government control on Sunday. Milad Hussein said rebels there and in other towns taken back in recent days were given the chance to surrender their weapons.

"If they did, they were left alone. If they didn't, there was an exchange of fire," he said.

Rebels said government forces conducted strikes on the town with aircraft, tanks and naval ships off the coast. One fighter who agreed to be identified only by a first name, Ahmad, said he was in Brega Sunday morning and retreated when the shelling intensified.

"There was a military order to fall back," he said, speaking by phone from the city of Ajdabiya, 50 miles (80 kilometers) to the east.

He said he heard later from other fighters that the government took control of the town.

With much of the fighting in the east taking place along a coastal highway bounded by strips of desert, there are few places for the rebels to take cover, forcing them to withdraw under fire before attempting to surge back.

A rebel soldier in charge of supplies, who insisted on speaking on condition of anonymity for fear of reprisals, also said their forces were now concentrated three miles (five kilometers) east of Brega in a seaside village. They hoped now to stop Gadhafi's forces from advancing to the next significant city to the east, Ajdabiya, he said.

Control of Brega was crucial because their forces had been using fuel from the site, he said. He claimed a government rocket hit a hospital in the onslaught, forcing doctors to evacuate the wounded.

"It's war, war, war, a fierce war," he said by phone, with explosions sounding in the background. "There's no protection. It hasn't stopped since this morning. There wasn't any time to breath, to do anything."

Also Sunday, Gadhafi's forces appeared to edge closer to Misrata, battling rebel fighters on the outskirts of Libya's third-largest city, 125 miles (200 kilometers) southeast of Tripoli, residents reported.

One resident, who did not want his name used because he fears for his safety, said streets inside his area of the city were empty as people took cover in their homes and the noise of tanks, anti-aircraft fire and machine guns grew ever-nearer.

He said several tank shells had struck inside the city, hitting a mosque and an apartment building.

Abdelfatih Ahmed of the rebel coalition in Misrata said another tank shell hit a residence for medical staff at the city hospital. He said some were killed and dozens were wounded, but he did not have precise figures.

A day earlier, the Libyan government took reporters from Tripoli, 375 miles (600 kilometers) east by plane and bus to show off its control of the former front-line town of Bin Jawwad, the scene of brutal battles six days earlier between insurgents and Gadhafi loyalists using artillery, rockets and helicopter gunships.

A police station was destroyed, its windows shattered and its walls blackened and burned. The inside was strewn with broken furniture. A nearby school had holes in the roof and a wall. Homes nearby were empty and cars were overturned or left as charred hulks in the road.

Rubble filled the streets and a sulfurous smell hung in the air.

The tour continued 40 miles (65 kilometers) to the east in Ras Lanouf, an oil port of boxy, sand-colored buildings with satellite dishes on top.

The area was silent and devoid of any sign of life, with laundry still fluttering on lines strung across balconies. About 50 soldiers or militia members in 10 white Toyota pickups, holding up portraits of Gadhafi, guarded the area. A playground was strewn with bullet casings and medical supplies looted from a nearby pharmacy whose doors had been shot open.

On Saturday, Al-Jazeera cameraman Ali Hassan al-Jaber was killed in what the pan-Arab satellite station described as an ambush outside Benghazi.

Correspondent Baybah Wald Amhadi said the crew's car came under fire from the rear as it returned from an assignment south of Benghazi. Al-Jaber was shot three times in the back and a fourth bullet hit another correspondent near the ear and wounded him, Amhadi said.

"Even areas under rebel control are not totally safe," he said. "There are followers, eyes or fifth columns, for Col. Gadhafi."

Hadid reported from Cairo. Associated Press writer Hadeel al-Shalchi contributed this report from Tripoli, Libya.