A Libyan rebel spokesman has claimed that a NATO air strike on the western city of Zlitan has killed Khamis Gaddafi, one of the sons of Libya's leader Muammar Gaddafi.
Mohammed Zawawi, a spokesman for the rebels, said on Friday that Khamis was among 32 people killed in the raid.
"Overnight there was an aircraft attack by NATO on the Gaddafi operations room in Zlitan and there are around 32 Gaddafi troops killed. One of them is Khamis," said Zawawi, a spokesman for the United Revolutionary Forces.
A NATO official at operations headquarters in Naples, Italy, told the Reuters news agency that while he was aware of the report, he could not confirm it.
"We cannot confirm anything right now, because we don't have people on the ground, but we are trying to find out what we can," he said.
"NATO struck an ammunition storage at around 8:15pm [1815 GMT] in Zlitan and a military police facility within a combat area at around 10:45pm [2045GMT] in the area of Zlitan yesterday," a NATO official told the AFP news agency, adding that it did not know if Khamis had been killed in those airstrikes.
According to NATO's regular operational media update, the alliance flew 117 sorties on Thursday, of which 44 were flown as "strike sorties", indicating that munitions were carried.
The targets hit included an "ammunition storage facility", a "military facility", two multiple rocket launchers and one surface-to-air missile system in Zlitan, the statement says.
It also said that it hit two "military facilities" in Tripoli, in addition to 11 other targets in various areas.
Reuters reported a Libyan government spokesman as denying the death of Khamis, terming the report a "dirty trick".
"It's false news. They invented the news about Mr Khamis Gaddafi in Zlitan to cover up their killing," Moussa Ibrahim told Reuters in Tripoli.
"This is a dirty trick to cover up their crime in Zlitan and the killing of the al-Marabit family," he said, referring to a family the Libyan government says was killed by a NATO air raid on Thursday.
Zawawi said the report of Khamis Gaddafi's death was based on information from spies within the ranks of Gaddafi's forces.
Zeina Khodr reports from the Nafusa Mountains
Khamis, 28, is the commander of the Libyan army's 32nd Brigade, which rebels say has been at the forefront of the government's defence of Zlitan, the last major western town on the road to Tripoli from the rebel-held east of the country.
Al Jazeera's Andrew Simmons, reporting from Misrata, said that at the moment most indications pointed towards "this not [being] a valid claim".
"If anything the scepticism over this claim that Khamis is dead is growing all the time.
"It just doesn't really add up at this stage, for these reasons: NATO have confirmed that they've been attacking this area not only Thursday night and Friday morning, but also on Thursday - five attacks on Thursday and two overnight.
"But not at the command centre which one opposition spokesperson is claiming was hit by NATO," he said.
"You have to also add to this that we have had a claim before that Khamis has been killed by NATO, and it proved to be erroneous."
The Gaddafi government claims that NATO air strikes in Zlitan on Thursday killed a mother and her two sons.
Officials showed journalists the house they say was hit by NATO bombs.
A spokesman for the military alliance confirmed that an airstrike had taken place, but said that the bombs had hit a "command and control site".
"We always take seriously allegations of civilian casualties and are looking into it, but we have no evidence at this stage that this was caused by an air strike," he said.