Forces loyal to Muammar Gaddafi resumed attacks on rebels as France demanded Nato do more to destroy the Libyan regime's heavy weapons.
Several rockets struck Ajdabiya, the main point leading into the rebel-held east, and there was also shelling in Misrata, the only major city in the western half of Libya that remains under partial rebel control.
Weeks of fierce government bombardment of Misrata have terrorised the city's residents, killing dozens of people and leaving food and medical supplies scarce. International groups are warning of a dire humanitarian crisis in Libya's third-largest city.
"Unfortunately, with the long-range war machines of Gaddafi forces, no place is safe in Misrata," a medical official there said.
French Foreign Minister Alain Juppe said Nato's actions were "not enough" and that the alliance should be firing on the weapons being used by Gaddafi's troops to target civilians in Misrata.
Mr Juppe spoke the day after Libyan rebels rejected a cease-fire proposal by African mediators because it did not insist that Gaddafi relinquish power.
"Nato has to play its role in full. Nato wanted to take the military command of the operations," Mr Juppe said. He also urged the EU to do more to get humanitarian aid to Misrata.
France has played a particularly aggressive role in Libya in recent weeks, pushing diplomatically for a UN resolution to allow the international military operation and firing the first strikes in the campaign. France also was the first to recognise the Libyan opposition and to send a diplomatic envoy to the rebel-held city of Benghazi.
A Nato general rejected the criticism and said the alliance was performing well and protecting civilians.
Dutch Brig Gen Mark Van Uhm said the alliance was successful in enforcing an arms embargo, patrolling a no fly zone and protecting civilians. "I think with the assets we have, we're doing a great job," he said. Nato took over command of the operation over Libya from the US on March 31.