(recasts, adds court details)
TBILISI, Aug 12 (Reuters) - At least 150,000 Georgians cheered President Mikheil Saakashvili on Tuesday as he vowed to one day punish Russia for launching the biggest military attack on Georgia since it split from its giant neighbour.
Russia blames Saakashvili for starting the war over the breakaway region of South Ossetia on Aug. 7 but there was no hint of internal dissent in Tbilisi, where even the normally critical opposition have strongly backed the president.
People streamed down the side streets to see their president. Flanked by bodyguards, Saakashvili arrived about an hour after the start of the rally to applause and cheers.
"I promise you today, that I'll remind them of everything they have done and one day we will win," Saakashvili said.
The crowd roared: "Georgia, Georgia!".
Speakers shook with anger and denounced Russia's aggression while the crowd waved Georgian flags and posters depicting Russian Prime Minister Vladimir Putin as a terrorist.
One placard showed Putin in a mug shot. "Wanted: Crimes against humanity and the world," the caption said.
Georgia announced it has filed a lawsuit against Russia at the International Court of Justice charging ethnic cleansing, the secretary of Georgia's Security Council said on Tuesday.
The crowd was mix of different Georgians from pensioners, to businessmen, to students, to young reservists who had earlier been called up to fight the separatists and their Russian allies.
An elderly lady leaned on a fence and wept, a young woman wearing a Georgian soccer shirt waved the national flag.
Some people said they had never been to a political rally before but they gathered in front of Georgia's parliament to support their country and their leader.
"We are a united nation, everybody is supporting Saakashvili. He has defended our country," 28-year-old Arteym Oganeyzov said as he stood on a step overlooking the crowd.
"WILL GO TO WAR"
Georgia, which declared independence in April 1991 when the Soviet Union crumbled, is a nation of about 4 million people with a small U.S.-trained army. Russia, with a population of about 142 million has a huge, well-equipped military.
For the last few days Georgia's main television station has shown movies depicting small armies relying on courage and heroism to fight bigger forces -- like the film "The 300" which shows a band of Spartans fighting a huge Persian invading army.
"Russia started this war and Saakashvili had to defend us," Irma Revazishvili, 43, said at the rally.
Russian artillery and warplanes have pounded Georgia's army which has retreated and abandoned the town of Gori, about 30 km outside the breakaway region of South Ossetia -- a mountainous region outside Georgia's control for over a decade.
Russian President Dmitry Medvedev on Tuesday called a halt to military operations. But for the crowd gathered in the hot sun the Russians had not defeated their army.
"Saakashvili loves this country, he is our president," 22-year-old student Shako Vezirishvili said as he stood with a Georgian flag draped around his shoulders.
"If my country wants me to go to war, I will go." (Writing by Ron Popeski and James Kilner, editing by Mary Gabriel)
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