A US man sentenced to 35 years in jail for his role in the 2008 Mumbai attacks has been pardoned by an Indian court after he agreed to be a witness.

David Headley appeared before a court in Mumbai via video conference and agreed to give full details of the planning and execution of the attacks.

Headley, 52, pleaded guilty and co-operated with the US to avoid the death penalty and extradition to India.

More than 160 people were killed by gunmen in the November 2008 attack.

The Mumbai court told Headley that his pardon was conditional and it expected him to fully disclose all the information he had on the attacks.

He appeared before the court through a video link from an undisclosed location in the US.

"He has become a government witness. The court decided to pardon him because his testimony will give more details of the attacks. He will testify on 8 February," Indian prosecutor Ujjwal Nikam told journalists in Mumbai.

Headley's US lawyer John Theis told BBC Hindi that he did not "expect anything substantially different from what he (Headley) has already said and it will be consistent with his testimony in Chicago".

"It [Headley's pardon in India] also doesn't affect the 35 year jail term that he's serving in the US," Mr Theis added.

Headley was sentenced in the US in 2013 on 12 counts, including conspiracy to aid militants from the Pakistani group Lashkar-e-Taiba (LeT) which India blames for carrying out the attacks.

After initially denying the charges, he eventually pleaded guilty and co-operated with the US to avoid the death penalty and extradition to India.

He admitted to scouting potential target locations in Mumbai ahead of the attacks.

Headley was born Daood Gilani to a Pakistani father and American mother but changed his name to David Coleman Headley in 2006 "to present himself in India as an American who was neither Muslim nor Pakistani", US prosecutors had said.

Headley is alleged to have told US prosecutors that he had been working with LeT since 2002.

He was arrested by FBI agents in Chicago in October 2009 while trying to board a plane for Philadelphia.

The 60-hour assault on Mumbai began on 26 November 2008. Attacks on the railway station, luxury hotels and a Jewish cultural centre claimed 166 lives. Nine gunmen were also killed.

The only surviving attacker, Pakistani Mohammad Ajmal Amir Qasab, was executed in India last November.