MOSCOW, Feb 28 (Reuters) - Russia on Monday doubled down on the logic for sending its forces into Ukraine, saying Western arms supplies to Kyiv showed that Moscow was right to try to demilitarise its neighbour.

Kremlin spokesperson Dmitry Peskov accused the European Union of hostile behaviour towards Russia and said the arming of Ukraine was an "extremely dangerous and destabilising factor".

He was responding to the stepping-up of weapons supplies to Ukraine to help it defend itself against the biggest invasion of a European state since World War Two. Moscow says it is engaged in a "special military operation" to protect civilians.

In a briefing for reporters, Peskov said, without providing evidence, that many Ukrainians were being used as human shields in what he called a crime by Ukrainian nationalists. He described them as victims of their country's propaganda.

Peskov said most Russians had relatives in Ukraine, and their hearts were aching over what was happening there.

He declined to comment on casualties suffered by Russian forces, referring the question to the defence ministry.

He also declined to elaborate on President Vladimir Putin's instructions at the weekend for Russia's nuclear deterrence forces to be placed on a "special regime" of alertness, or to comment on whether there was a risk of confrontation between Russia and NATO.