Mikheil Saakashvili has accused Russia of occupying half his country in a "peace enforcement operation" that ended on Tuesday. Russia says it no longer considers Saakashvili a partner, following Georgia's offensive in breakaway Ossetia last Friday, which killed at least 1,600 people, most of whom were Russian citizens.
"As president of Georgia, I stand before you in very difficult circumstances... Yesterday I saw with my own eyes how we were bombed," he said.
Georgia will "continue to stand firm" against the Russian aggressors, the president told the crowd.
He also announced that his country would leave the Commonwealth of Independent States, and urged Ukraine to follow suit.
"We have decided that Georgia will leave the CIS," he said. "We urge Ukraine and other countries to also leave the Commonwealth of Independent States, which is dominated by Russia."
Excluding Georgia, the CIS has 10 full members - Armenia, Azerbaijan, Belarus, Kazakhstan, Kyrgyzstan, Moldova, Russia, Tajikistan, Ukraine and Uzbekistan.
Saakashvili said Georgia now considers Russian troops in the South Ossetia and Abkhazia, Georgia's other rebel region, to be occupiers.
"We have taken the decision to declare Russian armed forces in Abkhazia and South Ossetia occupying forces," he said.
Russia's foreign minister earlier on Tuesday highlighted the severity of the crimes committed by Georgian forces in their attack on South Ossetia, and said Russia can no longer negotiate with President Saakashvili.
"The best thing would be for him to resign," Sergei Lavrov said.
Saakashvili "has killed our [Russian] citizens, ordered the crushing of women and children by tanks, and the burning alive of a group of girls herded into a cattle shed," Lavrov said. "And not only did he do all this with a background of European flags, but he declared that he was safeguarding American values."
"The crimes committed by the Tbilisi regime in South Ossetia merit investigation at an international tribunal," he said.
