KABUL: A US-Afghan military operation backed by helicopter gunships freed more than 40 soldiers and police held captive in a Taliban prison in southern Afghanistan, officials said Friday, in a major raid against the resurgent Islamist group.

The operation was conducted Thursday in Nawzad district in the southern opium-rich province of Helmand.

“Afghan special security forces... conducted a helicopter assault mission in Nawzad,” the US military said in a statement. “After securing the prison, Afghan forces freed more than 40 prisoners comprised of Afghan Police, Afghan National Army and Afghan Border Police members.”

The statement did not say how and when the security personnel were taken hostage.

It was unclear what role US forces played.

The raid marks a rare success for Afghan forces struggling to beat back the stubborn insurgency rapidly expanding north from its southern hotbeds.

The insurgents captured northern Kunduz city for three days in September in a stinging blow to Afghan forces, who have largely been fighting on their own since the end of NATO’s combat mission last December.

The emboldened insurgents have stepped up attacks on government and foreign targets since they launched their annual summer offensive in late April.