Human rights lawyer Amal Clooney has attended a preliminary hearing on an appeal against the 13-year jail sentence of the former Maldives president and met with the country's attorney general to discuss his case.

Clooney is part of a three-member international legal team trying to secure Mohamed Nasheed's release.

Nasheed told the High Court on Wednesday that the prosecutor general had no authority to appeal, while the prosecutor said he appealed on behalf of the state.

Nasheed was sentenced to jail in March after a lower court found him guilty of terrorism for ordering the arrest of a senior judge in 2012.

The government later started negotiations with Nasheed's party, raising hopes of a pardon. The talks broke down after authorities decided to appeal the case in court.