NATO on Sunday acknowledged responsibility for an airstrike that Libya said killed nine civilians in Tripoli earlier in the day.
"A military missile site was the intended target of air strikes in Tripoli last night," NATO said in a statement. "However, it appears that one weapon did not strike the intended target and that there may have been a weapons system failure which may have caused a number of civilian casualties."
Earlier, the Libyan government accused NATO of deliberately bombing a residential neighborhood, adding to charges that the alliance is striking nonmilitary targets.
Journalists based in the Libyan capital were rushed by government officials to a neighborhood where rescue efforts were under way at a destroyed building, which appeared to have been partially under construction.
There were heaps of rubble and chunks of shattered concrete at the scene, which a large crowd of what appeared to be local residents were helping to clear. The neighborhood is known for anti-Gadhafi sentiment.
Government spokesman Moussa Ibrahim said the damage was caused by NATO rockets and bombs. He said there were no military facilities anywhere near the damaged building.
"There was intentional and deliberate targeting of the civilian houses," said deputy foreign minister Khaled Kaim during a visit to the site shortly after reporters arrived. "This is another sign of the brutality of the West."
After initially reporting seven dead, Libyan officials said nine civilians were killed.
"Basically, this is another night of murder, terror and horror in Tripoli caused by NATO," Ibrahim told reporters. Five families were living in the building which was hit, he said.
'Utmost care and precision'
Reporters reached the site about 90 minutes after hearing the explosion. On previous occasions when reporters have been taken to see fresh airstrikes, the ruins of shattered buildings were still smoking after being hit. There did not appear to be any smoke at the site.
NATO, which has a mandate to protect Libyan civilians, rejects allegations it targets civilians.
"We are conducting operations with utmost care and precision to avoid civilian casualties. Civilian casualties figures mentioned by the Libyan regime are pure propaganda," NATO spokeswoman Oana Lungescu said Saturday.
Journalists who were taken to a hospital were shown at least four people said to be killed in the strike, including two young children. It was not possible to independently verify the government's account of what happened. Foreign journalists in Tripoli are not allowed to travel and report freely and are almost always shadowed by government minders.
If confirmed, the incident would be a blow to NATO's campaign which is aiding rebels fighting the government of Moammar Gadhafi at a time when the Western alliance is debating how to sustain its mission.
Two weeks ago, Libyan government officials were accused by a staff member at the same hospital in a note passed to journalists of falsely labelling a child hurt in a car crash as the victim of a NATO attack.
On Friday, Prime Minister al-Baghdadi al-Mahmoudi accused NATO of a "new level of aggression," and claimed that the military alliance intentionally targeted civilian buildings, including a hotel and a university. He has called on the United Nations to take action to stop NATO's daily bombing runs.
Libya's Health Ministry says 856 civilians have been killed in NATO airstrikes since they began in March. The figure could not be independently confirmed. Previous government tolls from individual strikes have proven to be exaggerated.
Late on Saturday, NATO announced that it had mistakenly struck a column of Libyan rebel vehicles in an airstrike near an eastern oil town two days earlier and expressed regret for any casualties that might have resulted.
The alliance has accidentally hit rebel forces before in its air campaign to protect civilians in the civil war between Gadhafi's military and the fighters trying to end his more than four decades in power.
The rebels also have complained that NATO's strikes have not helped them gain decisive momentum against the Libyan leader's better trained and equipped military, which still has firm control over most of western Libya. The rebels control much of the east.
The alliance statement gave no figures on casualties from Thursday's airstrike, but said it regretted "any possible loss of life or injuries caused by this unfortunate incident."
NATO said its forces spotted a column of military vehicles near the frequent flashpoint town of Brega where forces loyal to Gadhafi had recently been operating and hit them because they believed they posed a threat to civilians.
International military forces have had some trouble in hitting government troops because of their proximity to civilians. Gadhafi's troops have also used civilian vehicles, making them difficult to distinguish from rebel forces.
Shifting front lines
A doctor in the nearby city of Ajdabiya said the bodies of four rebel fighters were brought to his hospital around the time of Thursday's strike, but it was not possible to confirm whether they were killed in the bombardment.
A rebel military spokesman, Abdel-Rahman Abu-Sin, said Saturday that they appreciated NATO's efforts and understood the difficulty in differentiating between the two sides along shifting front lines.
Thursday's airstrike was similar to one in April during which NATO hit a convoy of rebel tanks, killing at least five fighters. NATO officials said at the time they did not know the rebels had any tanks, a statement that raised eyebrows as footage of the fighters with tanks had been on YouTube for weeks.
A coalition including France, Britain and the United States launched the first strikes against Gadhafi's forces under a United Nations resolution to protect civilians on March 19. NATO, which is joined by a number of Arab allies, assumed control of the air campaign over Libya on March 31.
Senior delegates from the Arab League, the European Union and the African Union along with envoys from the U.N. and the Organization of the Islamic Conference met in Cairo to review the developments in Libya.
Arab League chief Amr Moussa said the NATO mandate is not about bringing down Gadhafi's regime and a political solution is urgently needed.
"The situation has gone beyond what was expected. It is only natural that we speed up the search for a political solution and achieving a cease-fire," he said.
Meanwhile, four rebel fighters were killed on Sunday when their positions west of Misrata came under artillery fire from troops loyal to Gadhafi, Reuters reported.