The protest came as a top Russian general said his country's forces would keep patrolling Poti even though it lies outside the areas where Russia claims it has the right to station soldiers in Georgia.
On Saturday afternoon, several thousand protesters waving Georgian flags approached a Russian position on the outskirts of Gori. Some soldiers came out of their trenches, but there was no immediate sign of unrest.
"Russian military: You are not a liberating military, you are an occupying force," one man was heard shouting.
Russian troops were taking positions Saturday in trenches they had dug near a bridge that provides the only access to Poti. Tanks and APCs were parked nearby. They had hoisted both Russian flags and the flag of the Commonwealth of Independent States, or CIS, the union of former Soviet republics that Georgia recently announced it had left. Emotions ran high, though direct confrontation was avoided.
"They have the CIS flag, and that flag is not our Georgian flag," said one protester, Sulkhan Tolordava. "Georgia is not a member of this organization, so the troops must leave very quickly," he said.
Russia claims it is allowed to be in so-called "security zones" under peacekeeping agreements that ended fighting in the separatist Georgian regions of Abkhazia and South Ossetia in the 1990s.
While Poti is outside the buffer zone for the Abkhazia conflict, Col.-Gen. Anatoly Nogovitsyn said Russian troops who have set up positions on the city's outskirts won't leave and will patrol the city.
"Poti is not in the security zone. But that doesn't mean that we will sit behind the fence watch as they drive around in Hummers," Nogovitsyn said, referring to four U.S. Humvees the Russians seized in Poti this week.
The vehicles were used in joint U.S.-Georgian military exercises as U.S. trainers prepared Georgians for deployment to Iraq.
The United States, France and Britain protested that Russia has no claim to the alleged "security zones" under the cease-fire accord.
The Russians "have without a doubt failed to live up to their obligations," State Department spokesman Robert Wood said in Washington. "Establishing checkpoints, buffer zones, are definitely not part of the agreement."
Georgia's state minister on reintegration, Temur Yakobashvili, told the AP that formation of a buffer zone on Georgian territory outside South Ossetia "is absolutely illegal."
On Friday, Russia said it had pulled back forces from Georgia in accordance with a EU-brokered cease-fire agreement. Russia, though, interprets the accord as allowing it to keep a substantial military presence in Georgia - a point hotly disputed by the United States, France and Britain.
The Russian troop pullback allowed residents of the strategic central city of Gori to begin returning two weeks after they fled Russian air attacks and advancing troops. Chaotic crowds of people and cars were jammed outside the city Saturday as Georgian police tried to control the mass return by setting up makeshift checkpoints.
Those who were let through came back to find a city battered by bombs, suffering from food shortages and gripped by anguish.
Surman Kekashvili, 37, stayed in Gori, taking shelter in a basement after his apartment was destroyed by a Russian bomb. Several days ago, he tried to bury three relatives killed by the bomb, placing what body parts he could find in a shallow grave covered by a burnt log, a rock and a piece of scrap metal.
"I took only a foot and some of a torso. I could not get the other bodies out," he said.
His next-door neighbor, Frosia Dzadiashvili, found most of her apartment destroyed, leaving only a room the size of a broom closet to stay in.
"I have nothing. My neighbors feed me if they have food to share," the 70-year-old woman said.
Russian forces also set up a checkpoint near Senaki, the home of a major military base in western Georgia. Interior Ministry spokesman Shota Utiashvili said Russian soldiers had severely looted the base, taking away military equipment, televisions and even air conditioners.
In a separate development, a series of explosions rang out over the capital of South Ossetia, Tskhinvali, on Saturday. An AP reporter heard the blasts apparently emanating from a stash of weapons confiscated from Georgian troops. The cache is situated next to Tskhinvali's main hospital.
It remained unclear if arms were being deliberately destroyed. No casualties were reported.
Farther north of Tskhinvali, near the South Ossetian-Russian border, another AP reporter saw a convoy of about 150 Russian APCs, trucks and tanks by the roadside.
Russia's pullback on Friday came two weeks to the day after thousands of Russian soldiers roared into the former Soviet republic following an assault by Georgian forces on separatist South Ossetia. The fighting left hundreds dead and nearly 160,000 people homeless.
It also has deeply strained relations between Moscow and the West. Russia has frozen its military cooperation with NATO, Moscow's Cold War foe, underscoring a growing division in Europe.
President Bush, vacationing at his ranch in Texas, conferred with French President Nicolas Sarkozy and "the two agreed that Russia is not in compliance and that Russia needs to come into compliance now," said White House spokesman Gordon Johndroe on Friday.
"They have not completely withdrawn from areas considered undisputed territory, and they need to do that," Johndroe said.
The diplomatic struggle is certain to continue. The Russian parliament was expected to discuss recognizing the independence of the separatist regions South Ossetia and Abkhazia on Monday.
In an interview with the AP, South Ossetian leader Eduard Kokoity indicated that ethnic Georgians will not be allowed to return to their homes in South Ossetia.
"There is nothing left anymore" for them to come back to, he said.
There has been extensive looting and burning of Georgian homes in South Ossetia. In the village of Achabeti, an AP reporter saw Ossetians remove chairs, window frames and whatever else they could carry from abandoned Georgian houses.