It was a moment when the ceasefire between Russia and Georgia could have collapsed in a single nervous twitch of a soldier's trigger finger.

Opposing troops came within a hair's breadth of a firefight yesterday as a tense stand-off developed over the continued occupation of Gori by the Russian Army. Amid allegations that they were mining the city before a withdrawal, Russian tanks and troops continued to man checkpoints blocking access into the town.

They showed no sign of surrendering Gori to the Georgian authorities despite an earlier pledge to do so. Georgian police were admitted briefly to patrol Gori with Russian troops but retreated after relations between the two sides broke down.

The dramatic checkpoint confrontation occurred when a convoy of heavily armed Georgians in 20 pickup trucks approached the Russian position, apparently expecting their troops to be withdrawing.

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Instead, the Russians drew their weapons, prompting the Georgians to respond. The two sides confronted each other for several tense minutes until the Georgians retreated when Russian soldiers called up tank support.

The Georgians continued to watch nervously from a hill on the road 500 metres from the Russian line as Alexander Lomaia, the secretary of the National Security Council, approached to begin negotiations with the Russian commander on a withdrawal.

Mr Lomaia, dressed in a khaki flak jacket, said that the Russian troops were refusing to leave despite a previous agreement to do so, and that they would not withdraw from Gori until today at the earliest.

“We have to agree on the gradual deployment of troops and police in Gori. But there are mutual suspicions,” he said before travelling into the town with General Vyacheslav Borisov to continue the negotiations.

“They suspect that the forces we are deploying are not police forces. The separatists are trying to intervene and meddle in the situation. It is quite tense and the ceasefire is quite fragile.

“They promise to leave tomorrow. We have many reasons not to believe them but we try to help them to stick to what they have said.”

General Borisov took advantage of the opportunity to berate the international media at the checkpoint, accusing them of falsely reporting that Gori had been destroyed.

Red-faced with anger, he spluttered: “Do you see the city? Is it destroyed? We have not done anything.”

Fields were on fire outside villages close to Gori, however, and a plume of black smoke rose from behind a hill after an explosion. Later, more than 20 explosions and small arms fire were heard near the town.

Mr Lomaia persuaded the general to stop shouting and to travel together into Gori. Turning to reporters, he said: “He is going to kick you out of this place if he thinks that it's not stable.”

The Times witnessed at least seven Russian tanks and armoured personnel carriers blocking the route into Gori, with soldiers pointing weapons in the direction of the Georgian troops and media. Georgian army squads were stationed all along the route from Gori to Tbilisi and police had sealed off the road outside the capital to ordinary traffic.

Puffing on his pipe, an urbane defence attaché from a Western embassy was also on the scene to assess the latest military developments. Asked whether Georgia had given advance warning to his and other governments about the plan to invade South Ossetia, he replied: “I don't think any of us were told because if we had been we would have told them they were on their own.”

The delay in Russia's withdrawal was apparently linked to the reluctance of fighters from the breakaway enclave of South Ossetia to surrender control of Gori back to the Georgians and to retreat behind the border. Irregulars among the South Ossetians were continuing to steal cars belonging to Georgians, though one was returned later by a Russian officer.

Danish journalists said that drunken South Ossetia militiamen had fired shots into the ground before them, while another journalist had his TV camera seized.

Two vehicles from the United Nations High Commissioner for Refugees had been abandoned next to the Russian checkpoint and an official said that they had been blocked from entering Gori. A UN official said that the city was unsafe for aid officials to enter and that armed gunmen had stolen vehicles from UN staff.

The ceasefire brokered by President Sarkozy of France includes requirements for both sides to withdraw their troops, a ban on the use of force and free access for humanitarian aid. None of these conditions appeared to have been met yesterday.

A Georgian Interior Ministry spokesman said that Russian forces were destroying Gori, which lies about 50 miles north west of Tbilisi. But a Russian official rejected as an “absolute clear lie” allegations that troops were mining the city.

Even so, Vano Merabishvili, the Georgian Interior Minister, said that engineers and special forces were combing the area for Russian mines. He said: “We are cleaning roads because we have information that there are some mines.” President Saakashvili called on the West to send peacekeepers to protect Georgia from occupation. Writing in The Washington Post, he said: “Only Western peacekeepers can end the war. I have staked my country's fate on the West's rhetoric about democracy and liberty.”

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