Outside Tskhinvali, Georgia ? Russia and small, U.S.-allied Georgia headed toward a wider war Saturday as Russian tanks rumbled into the contested province of South Ossetia and Russian aircraft bombed a Georgian town and aircraft plant, escalating a conflict that already has left hundreds dead.

Georgia’s Foreign Ministry said the country was “in a state of war” and accused Russia of beginning a “massive military aggression.” The Georgian parliament approved a state of martial law, mobilizing reservists and ordering government authorities to work round-the-clock.

Russian President Dmitry Medvedev said that Moscow sent troops into South Ossetia to force Georgia into a cease-fire and prevent Georgia from retaking control of its breakaway region after it launched a major offensive there overnight Friday.

In a meeting with refugees, Prime Minister Vladimir Putin characterized Georgia’s actions as “complete genocide,” according to his office’s Web site. Putin also said Georgia had effectively lost the right to rule the breakaway province – an indication Moscow could be preparing to fulfill South Ossetians’ wish to be absorbed into Russia.

The risk of the conflict setting off a wider war also increased Saturday when Russian-supported separatists in another breakaway region, Abkhazia, also targeted Georgian troops by launching air and artillery strikes to drive them out.

Georgia President Mikhail Saakashvili called it an “unprovoked brutal Russian invasion.”

At a meeting of the U.N. Security Council Saturday, the third in three days on the issue, Russia refused to agree to a cease-fire or a diplomatic agreement. The move ensured that the fighting with Georgia would keep spilling into other regions such as Abkhazia’s Kodori Ridge.