Hundreds of US tanks, trucks and other military equipment have arrived by ship in Germany to be transported to Eastern Europe as part of a NATO build up that threatens to increase tensions with Russia.

Two shiploads arrived in the northern port of Bremerhaven on Friday and a third was due in a few days, while some 4,000 US troops will join up with the equipment over the next two weeks.

The forces will gather first in Poland, then fan out across seven countries from Estonia to Bulgaria as part of a series of measures aimed at reassuring US allies in Europe after Russia's 2014 annexation of the Crimea region of Ukraine.

"The best way to maintain the peace is through preparation," US Major General Timothy McGuire told reporters when asked if the large deployment was meant to send a message to Russia.

"This is just showing the strength and cohesion of the alliance and the US commitment to maintain the peace on the continent," he said.

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NATO countries say their planned deployments to eastern NATO countries are purely defensive, but Russia has rebuked what it sees as an aggressive Western build up in Eastern Europe.

In addition to US troops, NATO members Germany, Canada and Britain are also sending battalions of up to 1,000 troops each to the former Soviet republics of Estonia, Latvia and Lithuania.

They say the four battalions, backed by additional US forces on rotation, are justified by Moscow's annexation of Crimea and support for separatists in eastern Ukraine. Those actions alarmed the Baltic states, which worry they could be the next targets of Russian pressure.

Among their equipment will be 87 Abrams M1A1 tanks, 20 Paladin artillery vehicles and 136 Bradley fighting vehicles.

The equipment will be used by the US Army's 3rd Armored Brigade Combat Team, arriving this month from Fort Carson, Colorado, for the first of what Washington promises will be back-to-back nine-month rotations for the "foreseeable future".

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Germany's Left party, which has called for closer ties with Russia, said Berlin had a historic obligation to work for peace and disarmament, and it would protest against the deployment.

"Tanks never create peace anywhere," said Christian Goerke, who heads the party in Brandenburg state. "Quite the contrary, a troop deployment of such a scale is part of always increasing build up and provocation."

The military deployments came amid increased political tensions between Moscow and Washington, which accuses the Russian government of orchestrating cyber-attacks that allegedly influenced the 2016 US presidential elections and helped Donald Trump win the vote over Democratic candidate Hillary Clinton.

The US has imposed sanctions against Moscow over the allegations, expelling 35 Russian diplomats from the country.

Russia has denied interfering in the election.