SACHKHERE, Georgia — Russian forces on Wednesday built a sentry post just 30 miles from the Georgian capital, appearing to dig in to positions deep inside Georgia despite pledges to pull back to areas mandated by a cease-fire signed by both countries.

Russian President Dmitry Medvedev says his troops will complete their pullback by Friday, but few signs of movement have been seen other than the departure of a small contingent that have held the strategically key city of Gori.

A convoy of flatbed trucks carrying badly needed food aid to one of the areas most heavily hit by the fighting was waved through a checkpoint by Russian soldiers. And the U.S. State Department, meanwhile, said Turkey was allowing three U.S. military ships to pass through the Turkish Straits from the Mediterranean to the Black Sea to deliver humanitarian relief supplies to Georgia.

But conditions throughout much of Georgia remained tense.

Russian soldiers were setting up camp Wednesday in at least three positions in west-central Georgia. Further east, soldiers were building a sentry post of timber on a hill outside Igoeti, 30 miles from Tbilisi and the closest point to the capital where Russian troops have maintained a significant presence.

A top Russian general, meanwhile, said Russia plans to construct nearly a score of checkpoints to be manned by hundreds of soldiers in the so-called "security zone" around the border with South Ossetia.

And at a military training school in the mountain town of Sachkhere, a Georgian sentry said he feared Russian forces will make good on their threat to return after a confrontation the day before.

The sentry, who gave his name only as Corporal Vasily, said 23 Russian tanks, APCS and heavy guns showed up at the base on Tuesday and demanded to be let in. The Georgians refused and the Russians left after a 30-minute standoff but vowed to return after blowing up facilities in the village of Osiauri, he said.

Georgia's Defense Ministry said Wednesday that Russian soldiers destroyed military logistics facilities in Osiauri, but the claim could not immediately be confirmed.

"We're trying not to provoke them; otherwise they'll stay here for five to six months," Vasily said. He said the school itself had no heavy weapons or other significant strategic value, unlike the military base raided by Russians at Senaki, "where they even took the windows off the buildings."

Russia sent its tanks and troops into Georgia after Georgia launched a heavy artillery barrage Aug. 7 on the separatist, pro-Russian province of South Ossetia. Fighting also has flared in a second Georgian breakaway region, Abkhazia.