Russia staked an audacious claim to the vast mineral riches of the Arctic Ocean today when explorers planted their country's flag on the seabed below the North Pole.

In what Russian researchers had hailed as a symbolic mission to enlarge the country's territory "by more than one million square kilometres," two mini-submarines carried a total of six explorers to the ocean floor after a dive of 4,261 metres (13,980 feet) through a hole cut in the North Pole's icy surface.

After reaching their destination, the crew of one submarine left a one-metre Russian flag made of titanium and a capsule on the seabed.

The crew is the first to reach the seabed under the North Pole, and aims to strengthen Russia's claim to a swathe of ocean the size of western Europe that could contain billions of tons of oil and gas reserves.

The expedition plans to demonstrate that the Lomonosov Ridge, an underwater shelf that runs through the Arctic, is really an extension of Russian territory. The North Pole is believed to hold vast reserves of untapped oil and natural gas.

The Kremlin gave strong backing to the quest, which received huge coverage on state television. Vladimir Putin has also given Artur Chilingarov, who is leading the expedition and is Deputy Speaker of the Russian Parliament, the title of presidential envoy to the Arctic.

"Our mission is to remind the whole world that Russia is a great polar and research power," Mr Chilingarov said, as the submarines launched their expedition, which lasted almost nine hours.

Russia's Arctic and Antarctic Research Institute added: "Apart from the purely scientific goal of a comprehensive study of the climate and seabed at the North Pole, this expedition may help Russia to enlarge its territory by more than one million square kilometres."

However the mission of the two submarines, Mir-1 and Mir-2, was immediately mocked by Canada today, which described them as nothing more than a show.

"This isn’t the 15th century. You can’t go around the world and just plant flags and say 'We’re claiming this territory,'" Peter MacKay, Canada's Foreign Minister, told the country's CTV station.

Under international law, the five states with territory inside the Arctic Circle - Canada, Norway, Russia, the United States and Denmark via its control of Greenland - have a 200-mile economic zone around the north of their coastline.

Denmark and Canada have argued that the Lomonosov Ridge is connected to their territories and despatched a joint expedition last year to bolster their claims. Norway is also conducting a survey.

Canada's Prime Minister Stephen Harper ordered a new fleet of patrol vessels last month, saying they were needed to defend "our sovereignty over the Arctic". US politician have demanded action to defend its Arctic interests. Senator Richard Lugar warned in May that there would be no American presence at the negotiating table to challenge Moscow's claims unless the US ratified the Law of the Sea treaty.

Russia's Foreign Minister Sergei Lavrov said today that the success of the Arctic expedition would "supply additional scientific evidence for our aspirations", but that the issue would be resolved "in strict compliance with international law".

Mr Lavrov went on: "The expedition aims to prove that our shelf extends to the North Pole rather than at staking out Russia's claims."

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