Russian explorers dived deep below the North Pole in a submersible yesterday and planted their national flag on the seabed to stake a symbolic claim to the energy riches of the Arctic.

A mechanical arm dropped a specially-made, rust-proof titanium flag painted with the Russian tricolour onto the Arctic seabed at a depth of 4,261 metres.

"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 Mr Chilingarov, 67, also a top pro-Kremlin member of Parliament.

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.

But 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-kilometre 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.