Forces loyal to Moammar Gadhafi struck an oil pipeline and oil storage facility Wednesday, sending a giant yellow fireball into the sky as they pounded rebels with artillery and gunfire in at least two major cities.

Gadhafi appeared to be keeping up the momentum he has seized in recent days in his fight against rebels trying to move on the capital, Tripoli, from territory they hold in eastern Libya. State television claimed Gadhafi's forces had retaken Zawiya, the city closest to Tripoli that had fallen into opposition hands.

There was no was to immediately verify the claim. Gadhafi forces have been waging a heavy siege on the city since last week, and phone lines there have not been working for days. State TV showed a crowd of hundreds, purportedly in Zawiya's main square on Wednesday, carrying images of Gadhafi and shouting "The people want Colonel Gadhafi!"

The fall of Zawiya to anti-Gadhafi residents early on in the uprising that began Feb. 15 had illustrated the initial, blazing progress of the opposition, which has now been blunted.

In the east, an Associated Press reporter at Ras Lanouf near the front line of fighting saw an explosion from the area of the Sidr oil facility, 360 miles (580 kilometers) east of Tripoli. Three columns of thick smoke rose from the area, apparently from burning oil.

Mustafa Gheriani, an opposition spokesman, said the government artillery hit a pipeline supplying Sidr from oil fields in the desert. An oil storage depot also was hit, apparently by an airstrike, he said.

Gadhafi's successes have left Western powers struggling to come up with a plan to support the rebels without becoming ensnared in the complex and fast-moving conflict. On Wednesday, a high-ranking member of the Libyan military flew to Cairo with a message for Egyptian army officials from Gadhafi, but no further details were known.

President Barack Obama's most senior advisers were meeting Wednesday to outline what steps are realistic and possible to pressure Gadhafi to halt the violence and give up power.

They planned to examine the ramifications of a no-fly zone over Libya and other potential military options, U.S. officials said, speaking on condition of anonymity to discuss internal administration deliberations.

Britain and France are pushing for the U.N. to create a no-fly zone over the country, and while the U.S. may be persuaded to sign on, such a move is unlikely to win the backing of veto-wielding Security Council members Russia and China, which traditionally object to such steps as infringements on national sovereignty.