"They discussed the situation in Ukraine which is rapidly deteriorating," the Russian defence ministry said of Shoigu's call with French Defence Minister Sebastien Lecornu.Shoigu's ministry said he had told his French, Turkish and British counterparts of Moscow's concern that Ukraine could detonate a "dirty bomb" - a device laced with radioactive material.Previous Russian assertions that Ukraine might resort to using banned weapons such as biological arms have stirred concerns in the West that Moscow might be preparing to stage "false flag" attacks and blame them on Kyiv.The White House National Security Council in a statement said it rejected Shoigu's false allegations that Ukraine is preparing to use a dirty bomb on its own territory.Britain said Wallace had "refuted" claims by Shoigu that Western countries were facilitating a plan by Kyiv to escalate the conflict."