BRUSSELS - NATO said Saturday it 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 statement gave no figures on casualties from Thursday's airstrike, but said it regreted "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.

"NATO can now confirm that the vehicles hit were part of an opposition patrol," the statement said. There was no immediate comment from the rebel leadership.

Rebel spokesman Farag al-Moghraby said on Thursday the air strike took place near Ajdabiyah, eastern Libya, and that six rebel pickup trucks fitted with anti-aircraft guns had been destroyed.

Thursday's airstrike was similar to one on April 7 in which NATO hit a convoy of rebel tanks, killing at least five fighters, as the rebels were closing in on Brega. NATO officials said at the time they did not know the rebels had any tanks, a statement that raised eyebrows as footage of the rebels with tanks had been on YouTube for weeks.

A week earlier, NATO also mistakenly targeted rebels as they tried to retake Brega. The rebels said 13 of their fighters were killed in that attack.

NATO 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.

At least two explosions shook the capital, Tripoli, Saturday as NATO jets soared above the city, hours after Gadhafi lashed out against airstrikes in a speech Friday night, insisting "NATO will be defeated." It was not immediately clear what had been hit or if any casualties were reported.

In Brussels on Saturday, NATO spokeswoman Oana Lungescu dismissed Gadhafi's speech as "outrageous."

The alliance, which has a mandate to protect civilians, has been ramping up the pressure on Gadhafi's regime as a four-month uprising devolved into a civil war. Though most airstrikes happen under cover of darkness, daytime raids have grown more frequent.

Libya's Health Ministry released new casualty figures that put the number of civilians purportedly killed in NATO airstrikes through June 7 at 856. The figure could not be independently verified, and previous government-announced tolls from individual strikes have proven to be exaggerated. 

A coalition including France, Britain and the United States launched the first strikes against Gadhafi's forces  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 UN 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.