Libya has accused Nato of killing at least five people in an air strike that hit a house in the capital Tripoli.
A three-storey house was badly damaged at the scene of the alleged raid in the Souk al-Juma residential district.
Correspondents were later shown five bodies at a Tripoli hospital.
Nato says it destroyed a surface-to-air missile site in northern Tripoli overnight and is investigating the Libyan claims. Nato has previously admitted hitting mistaken targets.
Nato's Wing Cdr Mike Bracken told the BBC he did not know the exact location of the building Libyans accuse the alliance of hitting.
"Nato deeply regrets any losses of civilian life during [the Libya] operation, and it would be very sorry indeed if a review of this incident concludes it was a Nato operation.
"Our pilots and air crew go to great lengths to minimalise civilian risk, but ultimately you can never make that risk zero in a military campaign.
"Those areas that might have been claimed to be residential by the Gaddafi regime in the past have turned out to be being used as C2 nodes [command and control centres]."
If proved to be a Nato strike, the incident will raise more questions about the alliance's mission in Libya, says the BBC's Jeremy Bowen in Tripoli.
Our correspondent was taken by Libyan government officials to the site and later to a Tripoli hospital where he was shown the bodies of a dead woman, a dead man and a dead baby.
The officials said they were members of a family killed in the alleged Nato air strike.
Our correspondent was also shown the body of another man and a dead baby.
He saw two of the bodies earlier at Souk al-Juma - one was being pulled from the rubble and another was being placed in an ambulance.
Libyan officials say Sunday's attack, in one of the city's poorer neighbourhoods, happened shortly after midnight.
Scores of men were working alongside the emergency services, pulling at sections of rubble and looking for bodies.
Locals said an entire family had been killed, though our correspondent was unable to immediately verify this claim.
'Seed of hatred'
The level of damage, he adds, looked like the aftermath of an air strike, with concrete floors blown out onto the street - the incident did not look like a government stunt.
The site is about one mile from a military airfield which has been frequently targeted by Nato.
Libyan government spokesman Moussa Ibrahim said: "Nato is planting the seed of hatred in the hearts of Libyan people for years to come. They won't allow foreign armies to decide their future."
Deputy Foreign Minister Khaled Kaim told reporters at the site that this represented "intentional and deliberate targeting of civilian houses".
The incident occurred just over 24 hours after the country's prime minister accused Nato of specifically targeting civilians in its campaign.
Libyan rebels hold a third of the country in the east and pockets in the west, including Misrata, although Tripoli remains under government control.
Nato has flown more than 11,000 sorties since operations began, including almost 4,400 strike attacks against government targets across Libya.