"We strongly deny that this thing in Sorman is us," a NATO official said on condition of anonymity. "We have not been operating there."
The official, who spoke on condition of anonymity, said the only target in the Tripoli area overnight was a surface-to-air missile launcher in the capital itself which was struck at a different hour than claimed by the regime.
Libyan officials said 15 people, including three children, were killed in a NATO air strike at 4:00 am (0200 GMT) on Monday in Sorman, 70 kilometres (45 miles) west of Tripoli.
The new allegation came just hours after NATO acknowledged it was responsible for deaths in a residential area of Tripoli early Sunday. The regime said nine people were killed in that bombing.
Libyan government spokesman Mussa Ibrahim said the strike in Sorman hit the home of Khuwildi Hemidi, who served on the Revolution Command Council which Colonel Muamer Gaddafi established when he seized power in 1969.
A second Libyan official said Hemidi's home and two adjacent ones were hit by eight missiles in the 4:00 am (0200 GMT) strike in Sorman. Most of the dead were members of Hemidi's family. They included two of his grandchildren, the official said.
Rescue teams were still searching the wreckage for survivors as journalists were shown around the site at around midday (1000 GMT).