JOIN USThe rebels said two of their fighters and a paramedic were killed when NATO jets pounded them near the eastern oil town of Brega, less than a week after 13 people died in an alliance bombing in the same area.
"NATO is looking into the specific details of an alleged strike on a column of tanks outside of Brega today," the Western military organisation said in a statement.
"The fighting between Brega and Ajdabiya, where the strike occurred, has been fierce for several days. The situation is unclear and fluid with mechanised weapons travelling in all directions," it said.
"What remains clear is that NATO will continue to uphold the UN mandate and strike forces that can potentially cause harm to the civilian population of Libya," NATO said.
The 28-nation alliance took over military operations in Libya last week from a US, French and British coalition which had been enforcing a UN mandate to protect civilians in Libya since March 19.
NATO insists that it is not taking sides in the conflict and that its sole mission is to defend the population from attacks.
"Our focus is on protecting civilians against the threat of attack," NATO spokeswoman Oana Lungescu said earlier.
She also said it was difficult for NATO to confirm the reported strike "because we have no boots on the ground."
A day after it took charge, NATO warplanes killed nine rebels and four civilians near Brega last Friday after celebratory gunfire from insurgents prompted pilots to fire in self-defence.
The alliance has concluded that last week's bombing was an "unfortunate accident" and the rebels themselves admitted its fighters had made a "mistake" by firing tracers in the air.