Russia has warned it would act against rebel Chechen bases in neighbouring Georgia as part of the international fight against terrorism.
President Vladimir Putin said Russia had evidence rebels in Georgia's Pankisi Gorge helped plan last year's airliner attacks on the United States and were directly involved in 1999 apartment block blasts that killed about 300 Russians.
In a letter to U.N. Secretary-General Kofi Annan, Mr Putin said Georgia had turned a blind eye to rebel bases in Pankisi and shunned Russian offers to help flush out the militants.
"If the Georgian authorities do not undertake concrete actions aimed at destroying terrorists, and if militants continue their raids into Russia from Georgia, Russia . . . will undertake appropriate measures to counter this terrorist threat," Putin's letter said.
He said UN Security Council resolution 1368, voted after the deaths of 3,000 people in last September's attacks on the United States, gave Moscow the right to take action. But Mr Putin said that did not mean Russia would destroy Georgian sovereignty.
Georgian President Mr Eduard Shevardnadze responded by summoning security chiefs to an emergency meeting to discuss the Russian leader's order for Russia's military to draw up a hit-list of rebel bases on Georgian territory.