A day after arresting five Russian officers for spying, Georgia today demanded the handover of a sixth suspect, and kept up its blockade around the regional headquarters of Russian forces in Tbilisi, the Georgian capital.

The Georgian authorities said that they would maintain the blockade until Russia turned over the latest suspect.

Moscow reacted with fury to the arrests, describing them as a "complete outrage" and saying that Georgian authorities had produced no evidence that the officers in question were spies. Russian officials added that Georgia’s actions should be taken up by the UN.

Russian politicians have warned the Georgian government that they will use every means necessary to free a group of Russian army intelligence officers arrested for allegedly spying.

In a further response, the Russian Embassy in Tbilisi has stopped issuing visas, in a move certain to anger Georgians, many of whom travel to Russia for work and have relatives there.

The affair has plunged already tense relations between the small ex-Soviet state and its former colonial master to a new low.

Russia is alarmed by the pro-Western policies of President Mikhail Saakashvili, who came to power after Georgia’s Rose Revolution in 2003, on a pledge to free his country from Russian influence and develop relations with the West, including expressing a desire to join Nato.

Since then, Georgia has become the stage for increasing behind-the-scenes jockeying for influence between the US and Russia, although living conditions for most Georgians have changed little since the 1991 break-up of the Soviet Union.

Georgia in turn, has accused Russia of backing separatists in the provinces of Abkhazia and South Ossetia in an attempt to undermine the Government – an allegation which Russia denies. Only last Friday, President Saakashvili accused Moscow from the rostrum of the UN of trying to annex the breakaway provinces.

Georgian authorities confirmed that they had detained four men on charges of spying, with a fifth officer pulled in later. Vano Merabishvili, Georgia’s Interior Minister, said that a dozen Georgian citizens who were allegedly part of the same "very dangerous" spy chain had also been detained.

Mr Merabishvili said that the spy ring was led by a Russian agent, who allegedly staged a mine explosion in February 2005 which killed three police officers in the town of Gori. He added that the arrested suspects had shown interest in Georgia’s defence capabilities and its plans to join Nato, as well as energy security, political groupings and the country’s military.

Sergei Ivanov, Russia’s Defence Minister. called the charges absurd and demanded the officers’ immediate release. "I won’t be surprised if today the Georgian side files charges against them of wanting to steal the sun from the sky," he said, speaking on Russian television.

"All of this is aimed at provoking the situation and raising the degree of escalation to the maximum level in order to deflect attention from problems that exist in Georgia. Russia will react appropriately and responsibly."

According to some reports, he went to compare the arrests to repression by the Stalinist regime.

Sergei Lavrov, the Russian Foreign Minister, added: "We have demanded the immediate release of our citizens and we will achieve this with all the means available to us. This cannot be seen in any other way but as the latest example of an anti-Russian policy."

Mr Lavrov said that the case should be taken to the UN Security Council, and lashed out at Georgia’s increasingly warm relationship with Nato, saying it had served only "to intensify the anti-Russian policy" of the government in Tbilisi, according to local reports.

Officials in the small mountainous state in the Caucasus have been talking for weeks about a coup plot mounted by Russia against President Saakashvili.

Earlier this month, Georgian authorities arrested about 20 opposition activists on charges of plotting a foreign-funded coup. All were linked to a party whose fugitive leader has support in the Moscow establishment.

The Russian army still has two bases in Georgia - relics of Soviet times - which are to be withdrawn by bilateral agreement in 2008.

Times Recommends

• Air crash: ‘Everything is burnt. It is the closest thing to Hell’
• The true story of a passionate Korean 'spy'
• I shot Lennon in the back, Chapman tells parole board