Russian air attacks over northern Georgia intensified on Saturday morning, striking two apartment buildings in the city of Gori and clogging roads out of the area with fleeing refugees.

Meanwhile, Georgia threatened to pull out of the Olympic Games because of the Russian offensive in their country, their National Olympic Committee said on Saturday. Declaring a state of war, Georgia also called for a ceasefire on Saturday.

Russia said it had seized control of the rebel capital, Tskhinvali, but Georgia denied the claim on the second day of fighting that threatens oil and gas pipelines seen as crucial in the West.

Russian officials said the death toll now stood at 1,500 and 30,000 refugees from South Ossetia had fled to Russia over the past 36 hours.

Georgian forces shot down 10 Russian combat planes over the last two days, according to Alexander Lomaya, secretary of the Georgian National Security Council.

Shota Utiashvili, an official at the Georgian Interior Ministry, called the attack on Gori a “major escalation”, and said he expected attacks to increase over the course of Saturday. He said some 16 Russian planes were in the air over Georgian territory at any given time on Saturday.

In the Georgian capital of Tbilisi, wounded fighters and civilians began to arrive in hospitals, most with shrapnel or mortar wounds. Several dozen names had been posted outside the hospital.

In a news conference, the Russian foreign minister Sergei Lavrov said Georgian attacks on Russian citizens “amounted to ethnic cleansing”. Lavrov said Russian airstrikes targeted military staging grounds. Asked whether Russia is prepared to fight “all-out war” in Georgia, he said: “No. Georgia, I believe, started a war in Southern Ossetia, and we are responsible to keep the peace.” “We have been appreciative of the American efforts to pacify the hawks in Tbilisi. Apparently these efforts have not succeeded. Quite a number of officials in Washington were really shocked when all this happened.”