"It's mainly a show of solidarity toward our allies on the eastern flank near Russia," Defence Minister Odd Roger Enoksen told reporters.

The troops will be deployed immediately for a renewable three-month period.

The extra contingent is in addition to the 140 Norwegian troops already in Lithuania under German command, as part of NATO's "Enhanced Forward Presence" mission.

After Russia's annexation of Crimea in 2014, the Atlantic alliance deployed multinational battallions in Poland and the Baltic states as part of its reassurance mission.

Western nations fear a Russian invasion of Ukraine.

Moscow has denied plans to invade its neighbour but has massed more than 100,000 soldiers on their shared border.

Germany has also beefed up its contingent in Lithuania.

"A Russian attack against Ukraine may be imminent", Norwegian Foreign Minister Anniken Huitfeldt told the same press conference.

However, Moscow said on Tuesday that hundreds of its troops deployed for weeks near the Ukrainian border had begun withdrawing.

Norway is scheduled to host the Cold Response 2022 military exercises in the second half of March, NATO's biggest military manoeuvres in the Arctic since the end of the Cold War.

Some 35,000 troops are expected to participate.