Coalition warplanes have bombarded Libyan government positions for a fifth night - but have failed to stop Colonel Muammar Gaddafi's tanks shelling rebel-held towns.
The dictator's forces retained their strategic position in the east and have resumed their attack on the western city of Misratah.
And while the RAF said Col Gaddafi's air force effectively "no longer existed", residents said government snipers had continued indiscriminate firing across Libya's third largest city.
A rebel spokesman said the snipers had killed 16 people, while the regime's tanks were also said to be rolling back into the area.
"Government tanks are closing in on Misratah hospital and shelling the area," said a doctor in the city.
Col Gaddafi's officials claim a Western airstrike on a military base in the Tajoura district of Tripoli killed up to 19 people including civilians, and took film crews to a hospital to see the bodies of those they claimed were victims.
The US military denied the claims but said they had successfully established a no-fly zone over Libya's coastal areas and moved on to attack Col Gaddafi's tanks, with allies flying 175 sorties in 24 hours.
The UK launched further Tomahawk missiles at Libyan air defences from a submarine, said Major General John Lorimer, the Chief of Defence Staff's strategic communications officer.
Loud explosions were also heard in the Libyan capital Tripoli and smoke could be seen rising from an area where a military base is situated.
A resident, who did not want to be named, said: "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)."
A spokesman for the Libyan government denied its army was conducting any offensive operations and said troops were only defending themselves when they came under attack.
But a resident in Zintan, southwest of Tripoli, said Col Gaddafi's forces were bringing up more troops and tanks to bombard the rebel-held town.
Rebel forces in the east meanwhile were still pinned down outside the strategic junction at Ajdabiyah after more than three days of trying to recapture it.
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 TV station said.