The Libyan government renewed its artillery and rocket attack on the port of Misurata on Tuesday in its latest apparent attempt to cut the lifeline of the besieged rebel-held western city.

The fresh assault on the Mediterranean port killed a migrant worker from Niger and wounded 11 people, said Khaled Abu Falgha, a doctor at the Hikma hospital there. It also disrupted humanitarian aid work and forced a Red Cross boat that had docked in the city to turn around, according to Human Rights Watch.

A rebel spokesman called the afternoon shelling by Gaddafi’s forces “murderous.”

“He’ll keep hitting the port,” Mohamed Ali said via Skype on Tuesday. “He wants to disrupt the flow of humanitarian aid and make Misurata’s port as unsafe as possible.”

Ali, who said he was at the port as the shells rained down, said the worker from Niger was killed while lining up to board an International Organization for Migration boat that had been expected to dock. By nightfall, the boat still had not docked, he said. The organization was making its fifth trip to evacuate stranded migrants from Misurata.

Another rebel spokesman, Bashir, told the Reuters news service that Gaddafi’s forces were using Grad missiles — Russian-made munitions fired in multiple rounds from launchers on the back of trucks — to attack the port. Three Libyans were also killed by government shelling in an eastern suburb, Falgha said, making it a quieter day in the city than many of late. At least 57 people died in shelling and fighting over the weekend.

More than 2,000 migrant workers are camped out in tents near the docks waiting for an escape from the war-torn city, 131 miles east of Tripoli. Many have been sleeping there for weeks, sometimes under fire.

Gaddafi’s renewed attempt to strangle Misurata comes after his military was forced out of the city center in fierce fighting over the past few days. Loyalist troops have responded to the setback by intensifying their rocket and mortar attacks on the city, including on residential areas, from their bases to the south and east.

In an irony, Gaddafi’s government complained this week that NATO was trying to strangle it by blockading the port of Tripoli and preventing humanitarian supplies from entering, in violation of U.N. Security Council resolutions.

A NATO spokesman said Tuesday that deliveries of food, medicine and humanitarian relief were not being turned away. The bloc also denied that a rocket attack on Gaddafi’s compound Monday was an attempt on his life.

“This is about command-and-control nodes, and not about individuals,” Lt. Gen. Charles Bouchard, the Canadian who commands allied operations for NATO, said in an Internet briefing in which he summed up the air campaign that began March 19.

The destroyed buildings included offices, a library Gaddafi was known to use and a meeting hall where he often receives visitors, including a recent mediation mission from the African Union. Libyan government spokesman Moussa Ibrahim said the strike was “worthy of the mafia, of gangs, but not of governments” and would not help protect civilians.

But Bouchard said the compound was essentially military and contained communications gear used to transmit orders to loyalist forces to attack civilians. The Obama administration also said Tuesday that NATO’s objective in Libya was not to kill Gaddafi but to protect civilians.

“The military mission in Libya is not regime change,” Jake Sullivan, a senior State Department official, told reporters, confirming that military officials had targeted command-and-control facilities.

“The degradation of those command-and-control sites is a part of the operation and part of the reason the opposition has had some success,” he said. The White House, meanwhile, has approved an authorization to send $25 million in nonlethal aid to Libyan opposition groups.

Also in Washington, British Defense Minister Liam Fox and Gen. David Richards, the British chief of defense staff, met with their U.S. counterparts to discuss ways to break the stalemate between Gaddafi’s forces and the rebels.

In a brief statement afterward, Fox said that NATO has “seen significant progress made in the last 72 hours” in Libya, citing the withdrawal by government forces from Misurata, as well as reports of the capture of “underage soldiers and foreign mercenaries.”

“This underlines the regime’s inability to rely on its own security forces,” Fox said.

Fox said that U.S. and British defense officials had “good discussions on how to better exploit emerging opportunities on the ground” but did not elaborate.

The airstrike on Gaddafi’s compound Monday and a separate strike on a Libyan TV broadcasting center underscored the partial shift in NATO’s focus to government installations in Tripoli instead of purely military targets in the field.

Overall, however, the number of NATO airstrikes in Libya has remained stable over the past two weeks. NATO reported flying 56 strike sorties Monday — an average number. Since April 17, the daily number of strike sorties has fluctuated between 50 and 62, according to figures released by NATO.

Libyan Foreign Minister Abdul Ati al-Obeidi called on the African Union to hold an emergency summit meeting to discuss how to deal with the NATO airstrikes, accusing the West of aiming “to punish Africa through Libya” and to “steal its wealth and colonize it again.”

His position drew some support from Russian Prime Minister Vladimir Putin, whose government abstained from voting on U.N. resolutions against Libya but who sharply criticized Monday’s attack in Tripoli and said it had gone beyond the mandate granted by the United Nations.

“They said they didn’t want to kill Gaddafi. Now some officials say, ‘Yes, we are trying to kill Gaddafi,’ ” Putin said during a visit to Denmark, Reuters reported. “Who permitted this? Was there any trial? Who took on the right to execute this man?”

Unlike U.N. peacekeeping missions, whose mandate has to be extended every 12 months, the resolution imposing a no-fly zone is open-ended, so Russia’s ability to block military action is limited. But Moscow could prevent further action by the Security Council against Libya or veto attempts to get tough resolutions passed against countries such as Yemen or Syria.

The alliance against Gaddafi was buoyed this week by Italy’s decision to allow its warplanes to conduct strikes against Libyan government forces, while the Arab League showed no sign of wavering Tuesday, condemning the use of force against pro-democracy demonstrators in several Arab countries and saying the protesters “deserve support, not bullets.”

In a rare statement on the unrest in the Middle East, the 22-member league did not single out any Arab country but said the uprisings that toppled autocratic rulers in Tunisia and Egypt and the protests in Syria, Libya and Yemen “point to a new Arab era . . . led by youths seeking a better present and a brighter future.”

The league said foreign ministers from its member nations would meet in Cairo next month to discuss the “serious situation.” Egypt’s official Middle East News Agency said the meeting would be held May 8.

Fadel reported from Benghazi, Libya. Correspondent Edward Cody in Paris and staff writers Craig Whitlock and Mary Beth Sheridan in Washington contributed to this report.