The fighting that began when Georgian forces tried to retake the capital of South Ossetia, a pro-Russian region that won de facto autonomy from Georgia in the early 1990s, appeared to be developing into the worst clashes between Russia and a foreign military since the 1980s war in Afghanistan.

Georgia’s president, Mikheil Saakashvili, declared that Georgia was in a state of war, ordering government offices to work around the clock, and said that Russia is planning a full-scale invasion of his country.

Russia's Prime Minister Vladimir V. Putin, eclipsing the authority of President Dmitri A. Medvedev, left the Olympics in China and arrived Saturday evening in Vladikavkaz, a city in southern Russia just over the border that is a military staging area. State-controlled news broadcasts showed Putin meeting generals, suggesting that he was in charge of the operations on Georgian soil.

Putin made clear that Russia now viewed Georgian claims over the breakaway regions within its borders to be invalid, and that Russia had no intention of withdrawing. “There is almost no way we can imagine a return to the status quo,” he said, according to Interfax.