MOSCOW, Russia (Reuters) -- Russian explorers have dived deep below the North Pole in a submersible and planted their national flag on the seabed to stake a symbolic claim to the energy riches of the Arctic.

The Akademik Fedorov research ship carried about 100 scientists to the region.

A mechanical arm on Thursday dropped a specially made, rust-proof titanium flag painted with the Russian tricolor on to the Arctic seabed at a depth of 4,261 meters (13,980 feet).

"It was so lovely down there," Itar-Tass news agency quoted expedition leader Artur Chilingarov as saying as he emerged from one of two submersibles that made the dive.

"If a hundred or a thousand years from now someone goes down to where we were, they will see the Russian flag," said Chilingarov, 67, a top pro-Kremlin member of parliament.

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Russia wants to extend right up to the North Pole the territory it controls in the Arctic, believed to hold vast reserves of untapped oil and natural gas, which is expected to become more accessible as climate change melts the ice.

President Vladimir Putin congratulated the expedition by telephone on "the outstanding scientific project," local agencies reported.

Boris Gryzlov, who heads the State Duma lower chamber of parliament and the pro-Kremlin United Russia party, hailed the expedition as "a new stage of developing Russia's polar riches."

"This is fully in line with Russia's strategic interests," local media quoted him as saying. "I am proud our country remains the leader in conquering the Arctic. I am proud United Russia members took part in this unprecedented mission."

Major Russian channels aired a message from the Russian crew manning the International Space Station who said "this achievement must inspire the younger generation".

Earlier on Thursday Canada mocked Russia's ambitions and said the expedition was 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'," Canadian Foreign Minister Peter MacKay told CTV television.

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 320-kilometer (200-mile) economic zone around the north of their coastline.

Russia is claiming a larger slice extending as far as the pole because, Moscow says, the Arctic seabed and Siberia are linked by one continental shelf.

"Then Russia can give foundation to its claim to more than a million square kilometers of the oceanic shelf," said a news reader for Russia's state news channel Vesti-24, which made the expedition its top news story.

Russian media have said the move could raise tension with the United States in a battle for Arctic gas.

"I'm not sure of whether they've put a metal flag, a rubber flag or a bed sheet on the ocean floor. Either way, it doesn't have any legal standing or effect on this claim," State Department deputy spokesman Tom Casey told reporters.

A Tass reporter on board the mission support ship said crew members cheered as Chilingarov climbed out of the submersible and was handed a pair of slippers.

"This may sound grandiloquent but for me this is like placing a flag on the moon, this is really a massive scientific achievement," Sergei Balyasnikov, spokesman for Russia's Arctic and Antarctic Institute, told Reuters.

Russia says the mission is intended to show that the Lomonosov ridge, a 1,800-kilometer underwater mountain range that extends under the Arctic to near the pole, is a geological extension of Russian territory.

It denied it was a land grab.

"The aim of this expedition is not to stake Russia's claim but to show that our shelf reaches to the North Pole," Foreign Minister Sergei Lavrov told reporters in Manila, where he is attending a regional security conference.

The Mir-1 submersible reached the seabed at 1208 Moscow time (0808 GMT) and returned to the surface exactly six hours later.

A second Russian submersible, manned by Swedish businessman Frederik Paulsen and Australian adventurer Mike McDowell, reached the seabed 27 minutes later. It reached a depth of 4,302 meters.

Soviet and U.S. nuclear submarines have often traveled under the polar icecap, but until Thursday none had reached the seabed under the pole. E-mail to a friend

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