By Maria Golovnina and Michael Georgy
TRIPOLI (Reuters) - Western warplanes hit military targets deep inside Libya on Thursday but failed to prevent tanks reentering the western town of Misrata overnight and besieging its main hospital.
Air strikes destroyed government tanks on the outskirts of rebel-held Misrata, but other tanks inside the city were not hit, a resident said, underling the difficulty of the U.N. backed military mission to protect Libyans from Muammar Gaddafi.
Gaddafi's tanks rolled back into Misrata under the cover of darkness and shelled the area near the hospital, which was also under fire from government snipers, residents and rebels said.
"The situation is very serious," a doctor in the western town said by telephone before the line was cut off.
A resident called Abdelbasset said 6,000 workers and family members from Egypt and other African countries were stuck in the port, under the eye of two Libyan warships which moved in on Wednesday. "They haven't attacked but if they do, the thousands of workers will be the first victims," he said.
The continued fighting has strained an international coalition set up to try to stop Gaddafi's assault on Libyans seeking an end to his rule, with a growing list of countries wary of attacks on ground troops that could kill civilians.
NATO members are still trying to resolve differences over the command and aims of the international operation in Libya.
Western forces, having taken out Libyan air defenses, moved deeper into Libya and on to other strategic infrastructure.
France said it had hit an air base in central Libya early on Thursday, the fifth night of air strikes by Western powers on Gaddafi's military and al Arabiya television said planes struck Sabha, a Gaddafi stronghold in southern Libya, on Thursday.
A Libyan official said fuel storage tanks and a telecommunications tower in Tripoli were among places hit by what state television called "colonialist crusaders." A target in the Tajoura district which a resident said was a military area was also hit twice on Thursday.
Libyan Deputy Foreign Minister Khaled Kaim said strikes had hit military and civilian compounds in the central Jufrah region and other targets in Tripoli, Misrata and south of Benghazi in the east, home to a emerging alternative government.
Libyan officials took Reuters journalists to a Tripoli hospital to see 18 male corpses, some charred beyond recognition, saying they were military personnel and civilians killed by Western bombing overnight.
It was the first time foreign reporters had been shown alleged victims of the airstrikes and it was not possible to verify how many were civilians. Libya says dozens have been killed; Western forces deny any have been killed in the strikes.
The United States says it has successfully established a no-fly zone over the Libyan coast, begun attacking tanks and now wants to hand leadership of the mission to NATO.
"I think this is going to be a matter of days in which you see a movement toward the transition with regard to command and control," a top aide to President Barack Obama told reporters.
But NATO's 28 members have been unable to agree how to assume command of an operation whose final objectives remain unclear and face a fourth day of wrangling on Thursday with the main objections from Muslim member Turkey.
Seeking to allay fears of a protracted and bloody conflict, France said it could take days or weeks to destroy Gaddafi's military, but would not need months.
"You can't expect us to achieve our objective in just five days," Foreign Minister Alain Juppe told reporters.
British Foreign Secretary William Hague called for NATO to take over as soon as possible.
"The case for this action remains utterly compelling, appalling violence against Libyan citizens continues to take place exposing the regime's claims to have ordered a ceasefire to be an utter sham," he told parliament.
Turkey said it did not want NATO to take responsibility for offensive operations that could cause civilian casualties or be in charge of enforcing a U.N.-mandated no-fly zone while coalition aircraft were simultaneously bombing Libyan forces.
French Defense Minister Gerard Longuet said the U.N. resolution, "stipulates that the coalition has all means available to protect the civilians. What's threatening the population today is the tanks and artillery."
The Libyan government denies its army is conducting any offensive operations and says troops are only defending themselves when they come under attack.
Asked what should be done if the air strikes fail to restrain Gaddafi, only 7 percent of Americans favored sending in U.S. and allied ground troops in a Reuters/Ipsos poll released on Thursday, though 60 percent backed the no-fly zone.
Western commanders are hoping the rag-tag rebel force in eastern Libya will do the job for them but there is now little movement on the eastern front line at Adjabiyah, 150 km (90 miles) south of Tripoli.
The mood at rebel headquarters in Benghazi is muted after initial euphoria at sweeping almost unopposed through eastern Libya and winning the no-fly zone they had pressed for.
Mustafa Gheriani, a construction contractor-turned spokesman for the Benghazi administration, summed up the main problem -- the capital, which is still under Gaddafi's iron grip:
"We thought Tripoli would fall."
(Reporting by Mohammed Abbas and Angus MacSwan in Benghazi, Hamid Ould Ahmed and Christian Lowe in Algiers, Tom Perry in Cairo, David Brunnstrom in Brussels, Phil Stewart in Moscow, Andrew Quinn in Washington, Catherine Bremer, Emmanuel Jarry and Yves Clarisse in Paris; writing by Philippa Fletcher; editing by Giles Elgood)