Iran's former president Mohammad Khatami on Sunday asked Supreme Leader Ayatollah Ali Khamenei to intervene in the case of two reformist politicians who have been under house arrest without trial for the past six years, AFP reports.

Mehdi Karroubi and Mir Hossein Mousavi were reformist candidates during the 2009 presidential election, and questioned the shock victory of Mahmoud Ahmadinejad which led to mass protests.

A year later, in 2010, government forces firebombed the five-story Tehran home of Karroubi, and beat his bodyguard into unconsciousness.

The two have been under house arrest since 2011 for their part in the mass protests after the 2009 election.

Karroubi announced last December he would quit his party.

"I want to request the supreme leader to intervene to ensure that the house arrest is resolved," Khatami, who led a reformist government between 1997 and 2005, and is himself banned from appearing in the media since the protests, said on Sunday, according to AFP.

"The responsible institutions cannot or do not want to resolve the issue of the house arrests and only your intervention can allow this issue to be resolved, which is in the interests of the regime and would be a sign of its strength," he said, addressing Khamenei.

The issue has returned to the fore after Karroubi, 79, went on a brief hunger strike Wednesday to demand a trial.

He gave up the strike the following day after reportedly gaining assurances from the government that they would at least remove intelligence agents who had recently been posted inside his home.

On Sunday, however, the spokesman for the judiciary denied that the agents had been removed, saying this was "lies".

The fate of Mousavi and Karroubi played a significant role in the re-election of President Hassan Rouhani this May, with reformist voters chanting their names at his rallies.

Rouhani, despite being touted by the West as a “moderate”, did not act to release the two from house arrest despite promising to do so even during the 2013 election campaign.