Several "Taliban leaders" were among those killed in the pre-dawn attack in Kajaki district of province, Amir Mohammad Akhundzada, deputy provincial governor said.
"The Taliban were meeting in a mosque when the bombardment took place," Mr Akhundzada told Reuters by phone from Helmand.
"More than 50 of them have been killed."
Major Quentin Innes, a Canadian spokesman serving with the US-led troops in the south, said that up to 50 Taliban may have been killed when aircraft dropped two bombs on a compound, rather than a mosque.
He said the air attack was summoned after a group of Taliban ambushed a coalition convoy without managing to inflict any casualties. "The group then fled into a compound ... and we estimate that up to 50 of the attackers may have been killed," he said. Major Innes confirmed that a joint ground and air operation involving US-led and Afghan forces was going on in the district to hunt Taliban insurgents.
Two laser-guided munitions - $ 2.5 million
Two hand-held laser devices - $475
Fuel & maintenance on combat aircraft mission - $85,000
50 terrorists wiped out in seconds during a "mosque prayer" meeting - PRICELESS!!