Libyan rebels battling Muammar al-Qaddafi's troops along the country's Mediterranean coast said they have captured all of the strategic eastern port city of Brega, which has repeatedly changed hands in the 6-month-old civil war.

Rebel military spokesman Col. Ahmed Bani said fighters gained control Saturday of the industrial section of Brega, after having captured its residential areas last week.

Brega's capture is an important boost for the rebels. It contains Libya's second-largest hydrocarbon complex and is where the country's main oil fields feed into for refining.

"We have liberated Brega and all of it is under our control," Bani told The Associated Press on Saturday. "The fighters are in the port and taken the refineries."

Libyan leader Muammar al-Qaddafi's "back is against the wall" U.S. officials told Fox News, though it's still too early to tell whether rebel forces closing in on the capital Tripoli are close to ousting him.

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Qaddafi's troops seemed increasingly isolated in recent days, scrambling to use all force available to hold back rebels at the western front of the roiling civil war that has swept the country. Meanwhile, NATO has stepped up bombings in Tripoli, and rebels blocked supply route from Tunisia. A U.S. official confirmed to Fox News that “the squeeze is getting tighter” on Qaddafi -- and that he may simply abandon the country.

“The regime’s back is against the wall,” the official said, and the rebels are having success across the country including areas around Tripoli. Yet it remained unclear when exactly the Libyan leader would leave the country.

“When Qaddafi decides to go is in the mind of one man,” the top official told Fox News. But the overall message was clear: “It would not be a surprise if Qaddafi decided the time is up.”

The remarks clarify comments U.S. officials have made in past days about Qaddafi's plans, which still remain murky. Some reports point to him considering a move with his family, possibly for exile in Tunisia, for example.

The reports come as Pentagon officials described Libyan rebel gains as “significant developments” in the civil war that has engulfed the country.

On Wednesday, Pentagon spokesman George Little said that "the future doesn't look particularly bright for Qaddafi, but we'll have to see where things go."

He attributed the outlook to the rebel effort combined with sustained pressure from NATO operations and the economic and diplomatic sanctions.

Speaking at the National Defense University in Washington, D.C., on Tuesday Defense Secretary Leon Panetta said Qaddafi's days are numbered.

But on Thursday, the regime tried to dispute claims that the Libyan military was weakening.

"I want to assure you the Libyan government is still strong and resilient and is in control of the country and all its territory,” Prime Minister Baghdadi Ali al-Mahmoudi said. "Az Zawiyah is under our full control.”

"In terms of our military strength, we are powerful enough to finish this fight, but the cost in lives would be too high," he said referring to possible government counterattacks.

"We are a tribal people and the risk of this violence spreading is too great," said al-Mahmoudi..

Citing the increasing bloodshed the prime minister said it was "high time for a cease-fire."

NATO has been bombarding military targets in Libya since a no-fly zone was instituted in March. That includes areas near and in Qaddafi's sprawling Bab al-Aziziya compound, which is the Libyan leader's main headquarters and acts as a military barracks.

At least seven loud blasts were heard in Tripoli early Friday morning as bombs fell in the vicinity of Qaddafi’s main compound of Bab al-Aziziya.

An Associated Press correspondent staying in a hotel in the capital said he heard the explosions and saw flames in the air as bombs struck the ground. NATO jets were heard circling the sky above.

Residents in Tripoli also told The Associated Press that at least three blasts were heard on the road leading to the airport in the capital.

Just 30 miles to the west of the capital, opposition fighters in Libya's western mountains claimed control Thursday of the country's last functioning oil refinery, a significant blow to Qaddafi's regime.

The refinery is located in the strategic city of Zawiya, where rebels have made great strides in battles with government forces since their initial assault on Saturday.

A rebel victory in Zawiya could leave Qaddafi nearly cornered in his increasingly isolated stronghold of Tripoli, the capital, just 30 miles to the east along the Mediterranean coast.

Rebel fighters are now closing in on the capital from the west and the south, while NATO controls the seas to the north. The opposition is in control of most of the eastern half of the country and has declared Benghazi, 620 miles east of Tripoli, as its de facto capital.

Families fleeing their homes to avoid a possible rebel assault on Tripoli described growing tensions and deteriorating living conditions in the capital: Security forces have blanketed the city with checkpoints, gun battles are heard after nightfall and power outages last days.

Fox News' Justin Fishel and The Associated Press contributed to this report.