Afghan special forces backed by helicopter gunships freed more than 60 people held captive in a Taliban prison in southern Afghanistan, officials said Friday, in a major raid against the resurgent Islamist group.

The operation conducted Thursday in Now Zad district in the southern opium-rich province of Helmand comes in the midst of the Taliban's annual spring offensive, expected to be the bloodiest in 15 years.

‘Afghan Special Forces liberated over 60 prisoners from an illegally run Taliban prison... during the cover of darkness via helicopter assault,’ NATO said in a statement.

‘The liberated prisoners were safely transported to Kandahar where they were turned over to... Afghan authorities.’

NATO, which backed the mission in a ‘train, advise and assist’ role, added that two insurgents were killed during the operation, and many others were wounded and detained.

Afghan forces, backed by US Special Forces, launched a similar raid in Now Zad in December, freeing more than 40 soldiers and police held in a makeshift Taliban prison.

The raids marks a rare success for Afghan forces struggling to beat back the stubborn insurgency.

The Taliban last month announced the start of their annual spring offensive, vowing ‘large-scale attacks’ across Afghanistan.

Afghan President Ashraf Ghani recently threatened diplomatic reprisals against Pakistan if it refuses to take action against insurgent havens on its soil.

His unusually strong remarks were in response to a Taliban assault on a security services office in the heart of Kabul, which left 64 people dead in what appeared to be the deadliest attack on the Afghan capital since 2001.

The carnage on April 19 cast a pall over international efforts in recent months to jumpstart Pakistan-brokered peace talks, which stalled last summer after the Taliban belatedly confirmed the death of longtime leader Mullah Omar.