Western warplanes have hit Libya for a fifth night, but have so far failed to stop Muammar Gaddafi's tanks from shelling opposition-held towns.

A loud explosion was heard in Tripoli, the capital, early on Thursday, and smoke could be seen rising from an area where a military base is situated.

"We heard another explosion just now. We see smoke rising. There are people on rooftops. It seems to be in a military area near the engineering college [in the Tajoura area]," one resident told Reuters news agency.

Eight explosions were also heard in the east of the capital late on Wednesday.

Libyan state television said Western planes had struck in Tripoli and in Jafar, southwest of the capital.

"Military and civilian targets were attacked by colonialist crusaders," the report said.

French warplanes launched missiles at an air base around 250km inland, military spokesman Thierry Burkhard said.

The US military said 14 Tomahawk missiles were launched overnight, while the US Africa Command in Germany said coalition forces also dropped bombs on targets.

Government officials have accused coalition forces of killing dozens of civilians, but have not shown reporters in the capital any evidence of such deaths. US military officials deny any civilians have been killed in airstrikes.

Some journalists were taken to a hospital early on Thursday morning and shown 18 charred bodies, which the government said were military personnel and civilians killed in the air strikes, Reuters reported.

Undeterred by raids

The US military said it had successfully established a no-fly zone over Libya's coastal areas and had moved on to attack Gaddafi's tanks.

The allies flew 175 sorties in 24 hours, and the US flew 113 of those, a US commander said.

Gerard Longuet, the French defence minister, said France had destroyed about 10 Libyan armoured vehicles over three days.

Undaunted by air strikes, pro-Gaddafi forces pressed ahead with their assaults on the towns of Misurata, Ajdabiya and Zintan.

Gaddafi's tanks rolled back into Misurata under the cover of darkness and began shelling the area near the main hospital, residents and opposition fighters said, resuming their attack after their guns were silenced on Wednesday by Western air raids. The city, around 200km east of Tripoli and home to a major oil refinery, remains of the the last opposition hold-outs in the west.

Government snipers in the coastal city, Libya's third largest, carried on firing indiscriminately, residents said. An opposition spokesman said the snipers had killed 16 people.

"Government tanks are closing in on Misurata hospital and shelling the area," a doctor in Misurata told Reuters on the phone before the line was cut off.

Four children were killed in the city on Tuesday as regime forces pressed their siege, a resident and a rebel spokesman said. It was impossible to independently verify the reports.

The Libyan government denies its army is conducting any offensive operations and says troops are only defending themselves when they come under attack.

But a resident in Zintan, 106km southwest of Tripoli, said Gaddafi's forces were bringing up more troops and tanks to bombard the opposition-held town. 

Pro-democracy fighters had pushed Gaddafi's troops out of the town on Tuesday after enduring heavy shelling the day before, said Gaetan Vannay, a Swiss journalist observing events there. Rebels managed to capture four tanks during their attack, he said.

Meanwhile in the east, opposition fighters were pinned down outside the strategic junction at Ajdabiya after more than three days of trying to recapture the city.

Ajdabiya, around 160km south of the opposition stronghold of Benghazi, is connected by a straight inland road to Tobruk, near the Egyptian border. Despite coalition air strikes targeting Gaddafi's forces along the road between Benghazi and Ajdabiya, rebel forces have been unable to retake the town.

Source: Al Jazeera and agencies