A technical failure in a NATO missile may have caused a number of civilian casualties in Tripoli, a spokesman said on Sunday.

The intended target during last night's strike in Tripoli was a military missile site, said Wing Commander Mike Bracken. However from our initial assessment of the facts it appears that one weapon did not strike the intended target due to a weapons system failure. This technical failure may have caused a number of civilian casualties.

Bracken said NATO regrets the loss of innocent civilian lives and takes great care in conducting strikes against a regime determined to use violence against its own citizens, he said.

NATO says it has conducted 11,500 sorties over Libya under operation Unified Protector.

NATO undertook the mission after the United Nations Security Council passed a resolution authorizing all necessary measures to protect civilians in Libya.

While the United States, Britain, and France backed the measure, Russia and China abstained from voting although the countries could have blocked the resolution.