BRUSSELS, Aug 5 (Reuters) - NATO said on Tuesday it was not aware of any troop buildup by its ally Georgia in or near the country's breakaway South Ossetia region and called on all parties to reduce tensions.

Russia said on Tuesday it would not remain indifferent if violence escalated in South Ossetia, given the presence of Russian citizens there, Interfax news agency reported, quoting a Russian diplomat.

NATO spokeswoman Carmen Romero said the alliance was closely following the situation.

"NATO has seen the reports of the violent confrontations in the Georgian region of South Ossetia in the last few days, which caused a significant number of casualties," she said. "We call on all parties to de-escalate the tensions."

Russian has accused Georgia of using excessive force in South Ossetia, but Romero said NATO was "not aware of any troop concentrations by Georgia in or near South Ossetia".

The breakaway region is at the centre of a row between Russia and Georgia, which NATO says will one day join the alliance. The West fears tensions could trigger conflict.

Moscow's accusations followed a weekend of clashes in South Ossetia, a mountainous region bordering Russia that broke away from Georgia after a war in the early 1990s.

Interfax quoted Russian special ambassador Yuri Popov as saying that, if events continued to develop according to a "worst-case violence scenario", Russia would not remain indifferent, given that Russian citizens lived in South Ossetia, especially in the conflict zone. (Reporting by David Brunnstrom)

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