Russian warplanes widened the offensive outside the immediate conflict zone to include strikes deep inside Georgia on the second day of fighting that threatens international oil and gas pipelines that bypass Russia.

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. Russia said two of its warplanes had been shot down and 12 of its soldiers had been killed.

Russia's military response to the crisis dramatically intensified a long-running stand-off between Russia and the pro-Western Georgian leadership that has sparked alarm in the West and led to angry exchanges at the United Nations reminiscent of the Cold War.

Georgian President Mikheil Saakashvili said he would ask parliament to approve the introduction of martial law. Russia accused the West of contributing to the violence by supplying Georgia with arms.

Ukraine, a former Soviet republic whose pro-Western government now aspires to membership of NATO and the European Union, had encouraged Georgia to carry out "ethnic cleansing" in South Ossetia, the Russian foreign ministry said.

Russia said its forces had taken the South Ossetian capital. "Tactical groups have fully liberated Tskhinvali from the Georgian military and have started pushing Georgian units beyond the zone of peacekeepers' responsibility," Tass quoted Russian Ground Forces commander Vladimir Boldyrev as saying.

"The town is destroyed. There are many casualties, many wounded," Russian journalist Zaid Tsarnayev said by telephone from Tskhinvali.

"I was in the hospital yesterday where I saw many civilian wounded. The hospital was later destroyed by a Georgian jet. I don't know whether the wounded were still there."

Fighter Jet

Russian jets carried out up to five raids on mostly military targets around the Georgian town of Gori, close to the conflict zone in South Ossetia, a Reuters reporter at the scene said. But he saw at least one bomb hit an apartment, killing five people.

In Gori, a woman knelt in the street and screamed over the body of a dead man as the bombed apartment block burnt nearby.

Further down the street a shocked old woman covered in blood stared into the distance and a man knelt by the roadside with his head in his hands.

Russia said the death toll in the two-day conflict had hit 1,500 and was rising, prompting warnings from President Dmitry Medvedev of a humanitarian catastrophe that Moscow was determined to halt by force.

"Our peacekeepeers and reinforcement units are currently running an operation to force the Georgian side to (agree to) peace," Russian news agencies quoted Medvedev as saying at a meeting with Defence Minister Anatoly Serdyukov.

"They are also responsible for protecting the population. That's what we are doing now," Medvedev added.

Russian troops poured into South Ossetia on Friday, hours after Georgia launched a large-scale offensive aimed at restoring control over the province it lost after a war in the early 1990s.

Russia is the main backer of South Ossetian separatists and the majority of the population, who are ethnically distinct from Georgians, have been given Russian passports.

Tbilisi accuses Russia of launching a war against it. Russia sent fresh reinforcements overnight, which according to Russian news agencies have reached the regional capital Tskhinvali where fierce battles rage.

The Russian military said more reinforcements were on their way and Russian Foreign Minister Sergei Lavrov said Moscow was not seeking all-out war with Georgia.

With Washington the main backer of Saakashvili, the US State Department called in a top Russian diplomat to urge Moscow to halt military involvement in the conflict that erupted in earnest late on Thursday night.