BREGA, Libya — Rebels held out today in part of a strategic oil port after fierce fighting with Moammar Gadhafi loyalists waging a heavy counteroffensive trying to push the opposition further east away from the capital.

Pro-Gadhafi forces barraged rebels a day earlier with an hourslong hail of rockets and tank and artillery shells in their strongest attempt yet to recapture the oil facility of Ras Lanouf, in central Libya. The assault sent hundreds of rebel fighters into a frantic retreat further east, fleeing in cars and pickup trucks fitted with heavy machine guns.

But some opposition forces — including special commando forces that defected to the rebellion — continued the battle into the evening. By sunset, the regime troops burst into the residential area of Ras Lanouf, forcing rebels there to pull back, said Ibrahim Said, deputy director of the main hospital in Ajdabiya.

The rebel forces continued to hold out in the oil facilities and industrial areas of Ras Lanouf, about 10 miles east of the residential area. Four people were killed and 42 wounded in Thursday’s fighting.

The powerful assault on Ras Lanouf underscored how Gadhafi’s forces have seized the momentum in the back-and-forth battle with rebels, being waged mainly along the country’s long Mediterranean coastline. In the uprising that began Feb. 15, nearly the entire eastern half of the coast fell into the hands of the opposition, along with several cities in the western half, close to the capital Tripoli, which remains Gadhafi’s strongest bastion.

But government forces have repelled the rebels attempt last week to march west along the coast and if they decisively take Ras Lanouf, they could threaten the opposition’s bastions further east.

In Washington, the U.S. director of national intelligence stressed that Gadhafi’s military was stronger than it has been described and said that “in the longer term ... the regime will prevail.” President Barack Obama has called on Gadhafi to step down, and the White House later distanced Obama from the director’s assessment.

The opposition, however, made some diplomatic gains. France became the first country to recognize the rebels’ eastern-based governing council, and an ally of President Nicolas Sarkozy said his government was planning “targeted operations” to defend civilians if the international community approves. U.S. Secretary of State Hillary Rodham Clinton said she would meet with opposition leaders.