Aug. 8 (Bloomberg) -- Russian Prime Minister Vladimir Putin said ``war has started'' over the breakaway region of South Ossetia as Georgian President Mikheil Saakashvili accused its neighbor of a ``well-planned invasion.'' Saakashvili said in a Bloomberg Television interview that his nation of 4.6 million people is ``fighting to secure its borders'' amid a ``full-blown military aggression'' involving thousands of Russian troops. Aerial bombings and widespread fighting in and around the region killed an unknown number of civilians and wounded ``scores'' more, Saakashvili said. Putin earlier today told George W. Bush in Beijing that ``volunteers'' were pouring over the border to help defend South Ossetia from Georgian forces, according to Putin spokesman Dmitry Peskov. ``War started today in South Ossetia'' when Georgia attacked Russian peacekeepers in the disputed region, Putin said. The Defense Ministry later said it deployed ``reinforcements.'' The ruble dropped the most against the dollar in 8 1/2 years and Russian stocks tumbled today on concern the conflict will worsen. The U.S., U.K., European Union and NATO, which Georgia is seeking to join, all called on both sides to end hostilities. South Ossetia, which has a population of about 70,000 and is less than half the size of Kosovo, broke away from U.S.-backed Georgia in the early 1990s and now is a de facto independent state with Russian peacekeepers and economic support. Fighting ...