The Libyan air force has bombed the oil refinery and port town of Marsa El Brega as battles between forces loyal and against Muammar Gaddafi continued to rage in several towns across the North African country.
"We just watched an air force jet ... fly over Brega and drop at least one bomb and huge plumes of smoke are now coming out," Al Jazeera's Tony Birtley said on Wednesday.
The warplane from Gaddafi's air force struck a beach near where the two sides were fighting at a university campus.
A witness said the blast raised a plume of sand from a dune but caused no casualties, apparently an attempt to scare off the anti-Gaddafi fighters besieging regime forces in the campus.
"All the fighters here are massing. We understand that something like 250-300 pro-Gaddafi fighters are inside Brega and they are being surrounded," our correspondent said.
The bombing of Brega and reports about the fall of Gharyan and Sabratha towns in the country's northwest to pro-Gaddafi forces came as Gaddafi appeared on state television once again.
Located between Gaddafi's hometown of Sirte - still under government control - and the opposition-held eastern port of Benghazi, Brega also sits near ethnic fault lines between tribes loyal to Gaddafi and eastern groups opposed to him.
"They tried to take Brega this morning, but they failed," Mustafa Gheriani, a spokesman for the February 17th Coalition, an anti-government group, told the Reuters news agency.
"It is back in the hands of the revolutionaries. He is trying to create all kinds of psychological warfare to keep these cities on edge."
Al Jazeera's Jacky Rowland, reporting from Benghazi, Libya's second largest city now controlled by rebels, described the situation in the Brega region as fluid.
"I think it's fair to say that here is a fair amount of fighting going on in that area," she said.
Earlier the Associated Press news agency quoted Ahmed Jerksi, manager of the oil installation in Brega, as saying that pro-Gaddafi forces took control of the facility at dawn without using force.
There were conflicting claims about the casualties from these battles.
Government forces were also reported to be battling to regain control of rebel-held towns close to Tripoli, trying to create a buffer zone around what is still Gaddafi's seat of power.
Our correspondent said an air raid carried out by forces loyal to Gaddafi reportedly targeted a weapons store about 6km outside the eastern town of Ajdabiya.
Witnesses told the Associated Press news agency that they saw two warplanes bomb the town's eastern outskirts at 10am local time.
They also said pro-Gaddafi forces were advancing on the town. "I see two jets bombing now,'' one witness said, speaking on the condition of anonymity.
Another witness said rebel forces were rushing to the western side of Ajdabiya to meet the advancing pro-Gaddafi force.
Libyan forces have launched repeated air raids during the two-week revolt but all of them have been reported to target facilities that store weapons in areas controlled by the rebels.
Plea for UN-backed strikes
Meanwhile, the rebel National Libyan Council in east Libya called for UN-backed air strikes on foreign mercenaries used by Gaddafi against his own people.
Hafiz Ghoga, a spokesman for the council based in Benghazi, told a news conference that Gaddafi was using "African mercenaries in Libyan cities" which amounted to an invasion of the oil producing North African nation.
"We call for specific attacks on strongholds of these mercenaries," he said, but added: "The presence of any foreign forces on Libyan soil is strongly opposed. There is a big difference between this and strategic air strikes."
Wednesday's developments come as the US sent warships to the region as part of a Western effort to pile more pressure on Gaddafi to stop his violent crackdown and step aside.
The destroyer USS Barry moved through the Suez Canal on Monday and into the Mediterranean Sea.
Two amphibious assault ships, the USS Kearsarge, which can carry 2,000 marines, and the USS Ponce passed through the canal on Wednesday.
The White House said the ships were being redeployed in preparation for possible humanitarian efforts but stressed it "was not taking any options off the table".
"We are looking at a lot of options and contingencies. No decisions have been made on any other actions," Robert Gates, the US defence secretary, said.
The US says Libya could sink into civil war unless Gaddafi quits amid fears that the uprising - the bloodiest
against long-serving rulers in north Africa and the Middle East - could cause a humanitarian crisis.
Hillary Clinton, the US secretary of state, has cautioned that "Libya could become a peaceful democracy or it could face protracted civil war".
But Gaddafi remains defiant and his son, Saif al-Islam, has warned the West against launching military action, insisting that his father would neither step down nor go into exile.