The US is to deploy heavy weapons - including tanks, armoured vehicles and artillery - in a number of European nations, amid Nato concerns over Russia's role in Ukraine.

US Defence Secretary Ashton Carter said the equipment would be placed in Bulgaria, Estonia, Latvia, Lithuania, Poland and Romania.

Nato has vowed to boost defences in the east as ties with Russia have soured.

Russia has condemned the new Nato and US moves.

Responding earlier to reports of the planned deployment, Russian President Vladimir Putin accused Nato of "coming to our borders".

On a visit to the Estonian capital, Tallinn, Mr Carter said each set of equipment would be enough either for a military company, or about 150 soldiers, or a battalion - roughly 750 soldiers.

Much of the equipment was already in Europe, officials said.

In addition to the six nations, Germany will also take part in the expanded military effort, but already has the US materiel.