Western warplanes attacked Libya for a fifth night on Thursday, with the United States saying they have established a no-fly zone over coastal areas and are moving to attack army tanks.
However, they have failed to stop leader Muammar Gaddafi's forces shelling rebel-held towns or dislodge them from a strategic junction at Ajdabiyah in the east.
The international forces led by the United States, Britain and France began bombarding Libya on Saturday to enforce a United Nations Security Council resolution last week that set up a no-fly zone over the country and authorised the use of "all necessary measures" to protect civilians.
Residents and rebels say tanks rolled back into the city of Misrata under the cover of darkness and began shelling the area near the main hospital. They say sniper fire has killed 16 people, Reuters reports.
A loud explosion was heard in the capital Tripoli early on Thursday and smoke could be seen rising from an area where a military base is situated.
Libyan officials have taken foreign journalists to a hospital in the capital Tripoli to see what they say are the charred bodies of 18 military personnel and civilians killed by Western missiles.
The US military said it had successfully established a no-fly zone over Libya's coastal areas and had moved on to attack Colonel Gaddafi's tanks.
In 24 hours, the coalition has flown 175 sorties over Libya, including 113 of them by US planes.
The commander of British aircraft operating over Libya says Colonel Gaddafi's air force has been crippled.
Air Vice Marshal Greg Bagwell says it no longer exists as a fighting force and the allies can now operate with near impunity over the skies of Libya.
The Libyan government denies its army is conducting any offensive operations and says troops are only defending themselves when they come under attack.
Colonel Gaddafi says his forces will keep fighting and has urged what he called all Islamic armies to join him, saying: "We will be victorious".
Meanwhile, NATO countries have failed to agree on the Western military alliance taking over command of military operations in Libya from the US.
A NATO diplomat says no decision had been made after ambassadors of the 28-nation alliance held a third day of meetings in Brussels on Wednesday.