Russia's recent claims to vast swaths of the resource-rich Arctic highlight the need for Canada to defend its sovereignty in the region, Prime Minister Stephen Harper said Thursday.

While saying he doesn't know exactly what to make of Russia's latest move -- placing a Russian flag on the sea floor beneath the North Pole -- he said it shows Canada can't be complacent about the North.

"It shows once again that sovereignty over the North and sovereignty in our Arctic is going to be an important issue as we move into the future," Harper told reporters after a Conservative caucus meeting on Thursday in Charlottetown, P.E.I.

"This government has put a real emphasis on northern and Arctic sovereignty and we will continue to do so and we will move quickly in that regard."

The government plans to spend $7.5 billion to build and operate up to eight Arctic patrol ships in a bid to help protect northern sovereignty.

Earlier Thursday, Foreign Affairs Minister Peter MacKay dismissed the Russian move, calling the flag-planting tactics "just a show."

Russian explorers dived deep below the North Pole in a submersible on Thursday and planted a national flag on the seabed to stake a symbolic claim to the oil and gas wealth beneath the Arctic Ocean.

A mechanical arm dropped a rust-proof titanium Russian flag onto the Arctic seabed at a depth of 4,261 metres, Itar-Tass news agency quoted expedition officials as saying.

"Look, this isn't the 15th century. You can't go around the world and just plant flags and say 'We're claiming this territory,'" MacKay told CTV's Question Period co-host Jane Taber.

The foreign affairs minister asserted that there was no threat to Canadian sovereignty in the Arctic, despite the latest claims by Russia.

"Our claims over our Arctic are very well-established," MacKay said in Charlottetown.

While Mackay hasn't been in direct communication with his Russian counterpart, Foreign Minister Sergei Lavrov, he said Ottawa was making regular contact with Russian officials through the embassy.

The Rossiya atomic icebreaker plowed a route to the North Pole through a sheet of multi-year ice, paving the path for the Akademik Fedorov research ship to follow, said Sergei Balyasnikov a spokesperson for the Arctic and Antarctic research institute that prepared the expedition.

The voyage, which is led by polar explorer and Russian legislator Artur Chilingarov, also has some scientific objectives, including the study of Arctic plants and animals.

But the main goal appears to be strengthening its legal claims to the resources believed to lie beneath the Arctic sea floor.

The symbolic gesture of dropping the Russian flag onto the seabed, is intended to bolster Moscow's claims to about 1.2 million square kilometres of the Arctic shelf.

According to some estimates, it may contain about 9 billion tonnes of oil and gas deposits.

Russia's expedition is partly over oil, but it is also symbolic, says Michael Byers, academic director at The Liu Institute for Global Issues.

The U.S. Geological Survey estimates that 25 per cent of the world's undiscovered oil and gas reserves are on the floor of the Arctic Ocean. But it is also about Russian domestic politics and international politics," Byers told CTV Newsnet.

"The Russian government seeks to remind people that Russia is a powerful country. ... This move to put a titanium flag on the floor of the ocean under the North Pole is a pretty impressive technological feat, even if it has no legal consequences."

About 100 scientists aboard the Akademik Fedorov are looking for evidence that the Lomonosov Ridge, a 2,000-kilometre-long underwater mountain range that crosses the polar region, is a geologic extension of Russia, and therefore can be claimed by it under the UN Convention on the Law of the Sea.

"What Russia is doing in terms of collecting scientific evidence concerning the character of the seabed is actually part of a process at the United Nations whereby countries can claim continental shelves beyond the 320-kilometre mark," Byers said.

Moscow has claimed the polar region since at the least the days of the Bolsheviks.

In 2002, Russian officials argued to the United Nations that there was geological data backing their claim that the Arctic seabed and Siberia are linked by one continental shelf.

The UN dismissed Moscow's application then, citing lack of evidence, but Russia is expected to try again in 2009.

The expedition reflects an intense enmity between Russia, the United States, Canada and other countries -- whose shores face the polar ocean for the Arctic's icebound riches.

Last month, Ottawa said it would build up to eight patrol ships designed to operate in the frozen region in a bid to help protect its sovereignty.

"I think this is an opportunity for Canada to engage in some pro-active diplomacy and also to make its own contributions to this United Nations process by giving more money, more equipment to Canadian scientists so that they can match the Russian efforts on the Canadian side of the North Pole," said Byers.

With files from The Associated Press and The Canadian Press