Experts said they believed that with modern testing technology, the Russian authorities should know the answer by now.

But, increasingly, Moscow is deploying its new jet-powered drones, for which Ukraine also has limited answers. The drones now attack around the clock, targeting major businesses, data centres, railway infrastructure, medical facilities and densely populated residential neighbourhoods.

Perspective: Pneumonic plague sounds like the nightmare scenario. Strangely, it may be the more reassuring one.

Britain unveiled sanctions targeting Russian oil companies, its shadow fleet of tankers and those accused of supplying the Kremlin with goods.

Trump says Putin agreed to supply over 300,000 tons of diesel fuel immediately, with millions more tons to follow as prices soar past $6 a gallon.

Moscow has spent years knocking on the doors of biological laboratories in Ukraine. It should start by opening its own.

A global treaty signed by 197 countries — including Russia — requires reporting any death that could be a sign of an outbreak to come.

New information around the death of a lab worker, including a statement that she had been vaccinated against the plague, came as U.S. officials demanded more data.

Russian authorities are keeping a tight lid on information about last week’s suspicious death of a lab worker in Siberia that has been surrounded by secrecy and claims that it could have been caused by pneumonic plague.