Russia symbolically staked its claim to billions of dollars worth of oil and gas reserves in the Arctic Ocean today when two mini submarines reached the seabed more than two and a half miles beneath the North Pole.

In a record-breaking dive, the two craft planted a one metre-high titanium Russian flag on the underwater Lomonosov ridge, which Moscow claims is directly connected to its continental shelf.

However, the dangerous mission prompted ridicule and scepticism among other contenders for the Arctic's energy wealth, with Canada comparing it to a 15th century colonial land grab.

Descending to 4,300 metres, the mini-subs Mir-1 and Mir-2 collected water and sediment samples from the seabed. Russian scientists hope the samples will shore up their claim that the ridge is an integral part of Russia.

If Russia's claim is approved by the UN, the country could gain rights over supplies of hydrocarbons that some experts put at 10bn tonnes. The ice cap is melting, making exploration and drilling for oil and gas easier.

Speaking from the three-person Mir-1 on the ocean floor to colleagues aboard the research ship Akademik Fyodorov, the expedition's leader, Artur Chilingarov, said it had been a "soft landing".

"There is yellowish gravel down here. No creatures of the deep are visible," he added. Shortly before the dive, Mr Chilingarov, 68, a veteran polar explorer, told reporters his mission was to prove "the Arctic is Russian".

Russian state television trumpeted the successful dive, saying Russia could soon lay claim to 460,000 square miles of underwater territory. Speaking on the sidelines of talks in Manila, the Russian foreign minister, Sergei Lavrov, said: "I think the expedition will allow us to get the extra scientific proof for what we are planning to achieve."

However, Moscow's stance riled other northern hemisphere countries with their own claims to waters around the North Pole.

"This isn't the 15th century. You can't go around the world and just plant flags and say: 'We're claiming this territory'," the Canadian foreign minister, Peter MacKay, told CTV television.

Mr MacKay predicted that the Russian expedition would not bear fruit, adding: "There is no threat to Canadian sovereignty in the Arctic ... we're not at all concerned about this mission. Basically it's just a show by Russia."

Under the UN convention on the law of the sea, the five states with territory inside the Arctic Circle - Canada, Norway, Russia, the US, and Denmark, via its control of Greenland - have economic rights over a 200-mile zone around the north of their coastline.

However, the convention is open to appeal, and several countries are disputing the limits of this zone.

Russia believes its Siberian shelf is directly linked to the Lomonosov ridge, an underwater mountain crest that runs 1,240 miles across the polar region. In 2001, Moscow submitted research findings to that effect to the UN, but they were rejected, and it is expected to resubmit its claim in 2009.

Kim Holmen, the research director of the governmental Norwegian Polar Institute, told the Guardian that Russia's confidence could be misplaced.

Asked whether sediment samples from the ocean bed could prove the Lomonosov ridge and the Russian continental shelf were one and the same, he said: "In the geological sense, yes, but in the cartographic and political sense, no.

"The United States and Europe were at one time connected, the Appalachians and the Scottish mountains are the same geological formation, but Scotland cannot claim the United States is part of its territory because of that. These samples cannot prove once and for all that the whole discussion is over".

Depth soundings and other data would also be needed to stake a claim, he said.

However, the sceptics held no sway in Russia as the country swelled with national pride. "This is a serious, risky and heroic mission," Sergei Balyasnikov, a spokesman for the Arctic and Antarctic Institute, said.

"It's a very important move for Russia to demonstrate its potential in the Arctic. It's like putting a flag on the Moon."

Mir-1 has now returned safely to the surface, having been lowered by derrick into freezing waters cleared by the icebreaker Rossiya. Mir-2 is expected to appear shortly afterwards.