“Even one single case that is not backed by serious proof could seriously damage Georgia and the current administration’s standing,” Interior Minister Vano Merabishvili told reporters.

The suspects, who include pro-Western President Mikheil Saakashvili’s personal photographer, are accused of collecting confidential material on the Georgian leader that was passed to Russian military intelligence.

Merabishvili said he could prove long-term contacts between Russian officers and the alleged kingpin of the spy ring, European Pressphoto Agency photographer Zurab Kurtsikidze.

“We have enough evidence that Kurtsikidze was in contact since 2004 with people we have established to be officers of the Russian military intelligence agency,” Merabishvili added.

The arrests have caused widespread unease in Georgia’s media community, with journalists holding a series of protests in recent days calling for the case, which has been classified as ‘secret’, to be opened up to public scrutiny.

After concerns were also raised by Western diplomats, the Georgian prosecutor announced on Wednesday that the trial would be largely open.

“The prosecutor’s office has petitioned the court to exclude from the public hearings only the minor part of evidence which include state secrets,” a statement said.

The photographers have been put under two months’ pre-trial detention. They could face up to 12 years in jail if convicted.

Ex-Soviet Georgia fought a war with neighbour Russia in 2008 and has regularly accused Moscow of running espionage operations on its territory.

Moscow has branded the latest arrests as symptoms of “anti-Russian hysteria”.