MOSCOW (AP) - Russian troops in the breakaway province of South Ossetia have been put on increased combat readiness amid rising tensions on the de facto border with Georgia, according to officials.

Andrei Nesterenko, the spokesman for Russia’s Foreign Ministry, said Tuesday the move was a response to Georgian "provocations" and meant to prevent more violence.

"The most important thing now is to prevent escalation and not to allow skirmishes to grow into bigger clashes," Nesterenko said.

The situation near South Ossetia has become increasingly tense as the first anniversary of the Russian-Georgian war approaches Friday, with Georgia and Russia blaming each other for provocations and intentions to resume fighting.

Russian President Dmitry Medvedev called U.S. President Barack Obama late Tuesday "to wish him happy birthday," and during the conversation the two leaders "discussed the situation in Georgia and the need to decrease tensions in the region," the White House said in a statement.

Obama "reiterated the importance of working through established crisis management mechanisms such as the Joint Incident Prevention and Response Mechanism and underscored the need for international monitors," the statement said.