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Benghazi, Libya (CNN) -- The head of the interim government in eastern Libya pleaded Wednesday for the international community to move quickly to impose a no-fly zone over Libya, declaring that any delay would result in more casualties.

"It has to be immediate action," Mustafa Abdul-Jalil told CNN in an exclusive interview in this eastern opposition stronghold. "The longer the situation carries on, the more blood is shed. That's the message that we want to send to the international community. They have to live up to their responsibility with regards to this."

After the uprising began February 15, Abdul-Jalil was among the government officials who broke with the regime. He has gone on to lead the opposition's National Transitional Council, a 31-member group representing most regions in Libya. The group has met in Benghazi, an eastern town that has become an opposition stronghold.

Libyan leader Moammar Gadhafi told a Turkish reporter in an interview Tuesday that the imposition of a no-fly zone would simply unite the Libyan people behind him. "They will be united against the new attempt for occupation and imperialistic interests and it will be clear that they are conspiring against Libya," he said. "It will also be clear that the intentions are to control Libya's oil, choke Libya's liberty, land and people."

Abdul-Jalil's remarks came shortly after Gadhafi's regime announced a reward for Abdul-Jalil's capture, branding him "an agent spy."

In an "urgent" banner on state television, the government said its General Administration for Criminal Investigation was offering 500,000 Libyan dinars ($410,900 U.S.) "for whoever captures and hands over" the "agent spy" Abdul-Jalil, and "another offer of 200,000 Libyan dinars ($164,300 U.S.) for whoever offers information leading to his actual arrest."

In a letter to the U.N. General Assembly, the transitional council asked that it be recognized as "the sole representative of all Libya." It also asked the international community to "fulfill its obligations to protect the Libyan people from any further genocide and crimes against humanity without any direct military intervention on Libyan soil." The letter, which was dated March 5, was made public Wednesday.

The move to target Abdul-Jalil came as Gadhafi fought to advance against rebels who have taken control of many parts of the country. On Wednesday, pro-Gadhafi forces launched fresh attacks on Ras Lanuf, using planes and heavy artillery in an effort to retake the eastern oil city.

Opposition fighters, armed with anti-aircraft guns and Soviet rifles, were outgunned by the heavily armed pro-Gadhafi forces.

CNN's Ben Wedeman reported that an intense artillery bombardment was under way on the western edge of Ras Lanuf, where ambulances lined up to the emergency ward at Ras Lanuf's only hospital to drop off the wounded.

More than 25 people were wounded, said Dr. Ali Al-Bart, at Ras Lanuf Hospital. "It's very bad, the situation is very bad," he said.

Opposition efforts remained, but appeared weak. Ahmed Faturi left his clothing store in Benghazi to carry a SAM-7 surface-to-air missile, but knew he had little chance of hitting a plane with it.

And he expressed little hope that a no-fly zone would ever materialize. "Just talk," he said.

A few days ago, the rebel forces were advancing steadily westward toward Gadhafi's stronghold in the capital city of Tripoli. But that advancement appears to have reversed.

In Ras Lanuf, an oil storage tank to the west was hit in the fighting, though it was not clear who was responsible. Libyan state television reported that "armed groups supported by al Qaeda blew up an oil tank as they withdrew from Ras Lanuf against the advancing Libyan armed forces."

The attack marked the first time since the rebellion began more than three weeks ago that Libya's oil infrastructure has been damaged.

Gadhafi has shown no sign of giving up. On state television, he again insisted Tuesday night that youths misled and drugged by al Qaeda were to blame for the fighting. "For them, everybody's their enemy," Gadhafi said. "They know nothing other than killing."

The speech was recorded earlier Tuesday when Gadhafi addressed a youth group of tribal supporters, urging them to defend Libya from those who envy its standard of living.

"They want to take your petrol," he said. "This is what America, this is what the French, those colonialists, want."

A private Libyan aircraft crossed Greek airspace Wednesday en route to Cairo, Egypt, and the pilot said there were two passengers on board, according to Greek civil aviation authorities. The pilot did not identify the passengers, aviation authorities said. Multiple media reports said the plane landed in Cairo.

The development raised questions about whether Libyan officials may have flown to Cairo.

On Tuesday, an opposition member said Gadhafi was negotiating an exit deal, but other opposition members and the government denied that.

In the fourth week of what has become a civil war, Gadhafi's regime has held on to the capital, while losing control to the opposition in some other areas. Benghazi, in eastern Libya, is an opposition stronghold.

People in some towns in the western part of the country told CNN Wednesday their areas were under rebel control.

In Zuwarah, two sources said the city, which is located between Zawiya and the country's western border, with Tunisia, was surrounded by Gadhafi supporters but most shops and banks were operating normally.

A witness described the scene as tense, with schools, government offices and businesses closed. Demonstrations were no longer being held because, the witness said, "There is no one to protest against."

Two Zuwarah residents said "messengers from Gadhafi" had warned local leaders Wednesday to surrender or face attack.

The "messengers" told the leaders that replacing the pre-Gadhafi regime flag in the city with the government's green flag would be interpreted as a sign of solidarity with the regime, the sources said.

They added that there had been implicit threats against Zuwarah to bomb two nearby facilities: a petro-chemical plant 15 kilometers away and a gas export facility 30 kilometers away.

In Zawiya, two sources said the fighting continued in the city center Wednesday, but to a lesser extent than on Tuesday. They said the opposition occupied the city center, which was surrounded by the military. On the outskirts of the city, pro-Gadhafi rallies were being held, they said.

But Libyan television reported that Gadhafi supporters were celebrating "the liberation of the town from the armed terrorist elements backed by al Qaeda" in the main square.

Access to the city was limited. A witness told CNN she tried to travel from Tripoli to Zawiya but was turned away at various checkpoints.

Communications were so difficult that CNN was not able to talk with anyone in the city. One Zawiya resident, who told CNN she had to make the 40-minute trip to Tripoli to make a phone call, said there had been no electricity in Zawiya for the previous day.

In addition, two medical clinics that were shut Tuesday by the military remained closed Wednesday, she said.

Another source who fled Zawiya Tuesday for the Tunisian border said many bodies in the city lay unclaimed because relatives -- fearing violence -- would not go to graveyards to bury them.

Residents of Zuwarah sent weapons, explosives, and medical supplies via a small boat to Zawiya, the witness said. The man who drove the boat dropped the supplies immediately upon arrival and fled out of fear.

Libyan state TV showed video of government supporters cheering in Zawiya's streets and hoisting the government flag on Wednesday.

Witnesses said fear remained widespread in the capital, where schools were closed. A resident said she called several banks to ask about taking out money but was told that there was a shortage of cash.

Nalut was under opposition control and calm Wednesday, a witness said. In Ajdabiya and Misrata, spokesmen for opposition groups said those towns remained under opposition control and were calm as well.

Two doctors in Misrata said medical supplies were in short supply. More than 80 people remained at Central Misrata Hospital recovering from wounds suffered Sunday in fighting, they said.

Libya's government sought Wednesday to influence international sentiment, announcing that Libya's secretary of state for international relations will travel to Portugal, Greece and Malta on an exploratory fact-finding mission that may include other destinations.

Libya has invited British, French, Dutch and German fact-finding teams to Libya to examine reports of aerial bombardment and massacres. Libya had received no response from any of the invitees.

The decision about whether to impose a no-fly zone is a complicated one, said Nicholas Burns, a former U.S. ambassador to NATO.

"There's no assurance that the imposition of even a no-fly zone would make a decisive difference in the battle," Burns said. "Gadhafi has ground forces. He has artillery, he has a mercenary army. That's 95 percent of the fighting under way in Libya."

And it would not prove to be a panacea, the head of the U.S. Marine Corps told lawmakers Tuesday. Marine Corps Commandant Gen. James F. Amos said that a no-fly zone would do little to thwart Libya's helicopters, which he called "their greatest threat."

A no-fly zone would typically be enforced by fighter jets whose speed and altitude make it difficult to target helicopters, which move low and slow, Amos said.

For its part, Libya said it was not misusing its air force. Any no-fly zone would be tantamount to an act of war, Libyan Deputy Foreign Minister Khalid Karim said Tuesday.

The military, he said, "are taking purely defensive positions; they are not taking offensive ones." He said the Libyan government has asked for international monitors to verify that assertion.

The protests against the 68-year-old Gadhafi began February 15 as anti-government demonstrators sought his ouster after nearly 42 years of rule.

Death toll estimates have ranged from more than 1,000 to as many as 2,000. And the war has forced out 215,000 people, many of them poor migrant workers who have been stranded at both the Tunisian and Egyptian borders, the U.N. refugee agency has said.

While many countries chartered planes and dispatched ships to whisk away their citizens to safety, those stuck at the border are sheltered in cramped, unsanitary quarters with little to eat.

The United Nations' special representative for children and armed conflict, Radhika Coomaraswamy, said her office had received unconfirmed reports of violence against children, "including killing and maiming and use of children as combatants and the denial of humanitarian access."

Valerie Amos, the United Nations under-secretary-general for humanitarian affairs and emergency relief coordinator, called for all Libyan civilians to be protected.

"I am deeply concerned about the reportedly indiscriminate nature of the fighting, and particularly the use of heavy artillery and aerial bombardments," she said in a statement. "We are also hearing reports of hospital closures at the very time when people most need medical care."

The U.N. World Food Programme has initiated a $39.2 million emergency operation intended to provide food to more than 1 million people in Libya, Egypt and Tunisia over a three-month period.

In the latest sign of international solidarity with the Libyan opposition, a group of people entered a home in London Wednesday owned by Saif Gadhafi, the Libyan leader's son who has spoken on behalf of the regime in recent weeks. They could be seen hanging a banner out an upstairs window with a picture of Gadhafi in a red circle with a line through it.

"Out of Libya," the sign says, "Out of London." London Metropolitan police said only the situation was "being treated as a civil matter."

CNN's Ben Wedeman, Whitney Hurst, Nic Robertson, Chris Lawrence, Arwa Damon, Salma Abdelaziz, Jomana Karadsheh and Caroline Faraj contributed to this report