Vladimir Putin visits a military training centre in Ryazan Region, Russia. Defence Minister Sergei Shoigu is on the left. AP

Russia continues to use Iranian uncrewed aerial vehicles (UAVs) against targets throughout the Ukrainian territory, the British Ministry of Defence said on Monday.

Russia is likely using the Iranian Shahed-136 UAVs to infiltrate Ukranian air defences and as a substitute for Russian-manufactured long-range precision weapons that are becoming increasingly scarce, the ministry said in its update on Twitter.

Ukrainian efforts to contain the UAVs have been successful, the ministry said.

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Meanwhile, Russia fired missiles and drones into the Ukrainian-held southern town of Mykolaiv, destroying an apartment block, and said the war was trending towards "uncontrolled escalation" in a flurry of telephone calls to Western defence ministers.

The strike on the shipbuilding town about 35 km (22 miles) northwest of the front line in Kherson came as Russia ordered 60,000 people to flee the region "to save your lives" in the face of a Ukrainian counter offensive.

Ukrainian Foreign Minister Dmytro Kuleba gestures during a press conference. File photo

Russian Defence Minister Sergei Shoigu discussed the "rapidly deteriorating situation" in phone calls with British, French and Turkish counterparts, the ministry said.

He also spoke by phone with US Defence Secretary Lloyd Austin for the second time in three days. The Pentagon said Austin told Shoigu he "rejected any pretext for Russian escalation."

Without providing evidence, Shoigu said Ukraine could escalate by using a "dirty bomb", or conventional explosives laced with radioactive material.

Ukraine does not possess nuclear weapons, while Russia has said it could protect its territory with its nuclear arsenal.

Ukrainian Foreign Minister Dmytro Kuleba rejected the accusation as "absurd" and "dangerous", adding: "Russians often accuse others of what they plan themselves."

In a joint statement after the talks, Britain, France and the United States said they were committed to supporting Ukraine "for as long as it takes" and rejected Russia's warning about a "dirty bomb".

"Our countries made clear that we all reject Russia’s transparently false allegations that Ukraine is preparing to use a dirty bomb on its own territory," they said.

"The world would see through any attempt to use this allegation as a pretext for escalation."