Russian explorers have planted their country's flag on the seabed 4,200m (14,000ft) below the North Pole to further Moscow's claims to the Arctic.
The rust-proof titanium metal flag was brought by explorers travelling in two mini-submarines, in what is believed to be the first expedition of its kind.
Both vessels have now rejoined the expedition's ships, completing their risky return journey to the surface.
Canada, which also claims territory in the Arctic, has criticised the mission.
"This isn't the 15th Century," Canadian Foreign Minister Peter MacKay told the CTV channel.
"You can't go around the world and just plant flags and say 'We're claiming this territory'," he said.
Melting polar ice has led to competing claims over access to Arctic resources.