The United Nations Security Council has met behind closed doors to discuss Russia's claim that Ukraine may use a so-called "dirty bomb." Western diplomats have described the assertion as unsupported and false.

Moscow requested an emergency Security Council meeting. The request was made after Russian officials expressed their concern that Ukraine could create a bomb designed to disperse radioactive material.

Sources say Russia reiterated the claim at Tuesday's meeting.

Dmitry Polyanskiy is Russia's first deputy permanent representative to the UN. He told reporters after the meeting that Ukraine has the ability, and every reason, to create a dirty bomb. Polyanskiy said the threat is very serious.

Britain's Deputy Permanent Representative to the UN James Kariuki said, "We've seen and heard no new evidence in this private meeting." He called Russia's allegation "transparently false."

Kariuki added, "And we should be clear, this is pure Russian misinformation of the kind we've seen many times before."

Norway's UN mission posted a message on Twitter. It said that Russia should stop spreading undocumented allegations.