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TBILISI, Aug 11 (Reuters) - A Georgian official said on Monday Russian forces had captured the Georgian town of Gori, 60 km (35 miles) from the capital Tbilisi, but Russia denied it and Reuters witnesses saw no troops in the town.

"They have captured the city of Gori," the secretary of Georgia's National Security Council, Kakha Lomaia, told Reuters by telephone.

Moscow swiftly denied the statement.

"There are no Russian troops in Gori," a Russian Defence Ministry spokesman said.

Gori, small town of about 50,000 people 25 km from South Ossetia and the birthplace of Soviet leader Josef Stalin, lies on the main road linking the breakaway province and the rest of Georgia.

Earlier, a senior Georgian security official said forces had deployed to positions behind Gori in case of a Russian attack on Tbilisi.

Georgian worries about an attack on the capital increased after Russian troops moved from another breakaway region, Abkhazia, into the town of Senaki in western Georgia.

Two Reuters reporters in Gori said they saw no evidence of a substantial Russian presence in the town.

One said he saw Georgian soldiers leaving in convoys.

The second reporters said: "We are right now driving through the town and I see no trace of troops or military vehicles. It is absolutely deserted."

The reporter said he later saw a Georgian armoured personnel carrier on fire east of Gori on the highway to Tbilisi. A long convoy of Georgian military trucks was heading away from Gori towards the capital. (Reporting by James Kilner and Margarita Antidze; editing by Andrew Dobbie)

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