WASHINGTON (AFP) - The Group of 7 (G-7) voiced concern about bloody violence and the build-up of weapons in eastern Ukraine Friday, days before a negotiated ceasefire was due to come into effect.

Welcoming a peace plan agreed between Russia and Ukraine, leaders of the group of industrialised nations called on all sides to refrain from moves that could scuttle the deal.

"All parties should refrain from actions in the coming days that would hinder the start of the ceasefire," the group said in a joint statement.

Ahead of a Feb 15 ceasefire, the G-7 said it was "concerned" about fighting around the eastern town of Debaltseve.

There, the group said, "Russian-backed separatist militias are operating beyond the line of contact" agreed in a largely ignored 2014 agreement, "causing numerous civilian casualties."

At least 5,480 people have died in fighting that has ratcheted up East-West tensions to levels not seen since the Cold War.

"We urge all sides to adhere strictly to the provisions of the package and to carry out its measures without delay, starting with a ceasefire on the 15th of February," the G7 statement said.

The G-7 warned it was ready to "intensify the costs" for anyone who broke the terms of the agreement.

The United States earlier said it received reports that heavy weapons were being moved into eastern Ukraine from Russia over the past few days.

The State Department claimed Russian military had deployed large amounts of artillery and multiple rocket launcher systems and was using it to shell Ukrainian positions.

Russia denies aiding the separatists or being an active participant in the war.

The G-7 is made up of Canada, France, Germany, Italy, Japan, the United Kingdom and the United States - as well as representatives of the European Union.

Russia had been part of the then-G-8 before being kicked out after its annexation of Ukraine's Crimea region, which the G-7 described as being "in violation of international law."