Russia and Norway have ended a 40-year dispute and signed an agreement on where their Arctic borders should be drawn, opening the way to massive offshore oil and gas exploration.
President Dmitry Medvedev and Prime Minister Jens Stoltenberg presided over the signing in Murmansk.
The disputed territory covered 175,000 square km (67,600 sq miles), an area about half the size of Germany, mainly in the Barents Sea.
According to a Kremlin statement, any oil and gas fields straddling the border would have to be developed jointly.
Canada, Denmark Norway, Russia and the United States all want to file territorial claims over oil, gas and reserves of precious metal that could become more accessible as the Arctic ice cap shrinks.
International law states the five have a 320km economic zone north of their borders, but Russia is claiming a larger slice based on its contention the seabed under the Arctic is a continuation of its continental shelf.