What's Happening On The Georgia-South Ossetia Border?

For the past several days, South Ossetia's de facto government has been warning about a Georgian military buildup along its border. On Tuesday, South Ossetia's president said that "Georgia is preparing seriously for a war," building up fortifications and arms stores. The following day, an "analysis" by the de facto government's press service suggested that Georgian President Saakashvili was planning to provoke a war to boost his party's prospects in upcoming parliamentary elections. On Thursday, South Ossetia's Ministry of Foreign Affairs warned that Georgia was positioning heavy weaponry, including multiple-launch rocket systems and armored vehicles, along the border.

But now the European Union Monitoring Mission, which keeps track of events along the border, said there's no such thing -- and noted that in fact Russia is building up its own forces along the de facto border:

In recent days, there have been claims about a possible change in posture of Georgian security personnel at the South Ossetian Administrative Boundary Line. The EU Monitoring Mission has been intensively engaged in monitoring and assessing these reports with the deployment of extra patrols and has been checking the situation with the relevant authorities. The Mission has not observed any evidence to support these claims. However, EUMM has further increased its patrolling to actively monitor the situation on the ground.

The EUMM has at the same time observed a build-up of Russian Federation armed personnel along the South Ossetian Administrative Boundary Line. The Mission has raised its concerns about this activity with the relevant Russian command structures.

The EUMM urges all sides to refrain from any activities that could destabilize the security and safety of the local population on either side of the Administrative Boundary Line.

So what sort of Russian buildup is this? What's going on?