US President Donald Trump said it "certainly looks like the Russians were behind" the poisoning of a former Russian spy and his daughter in the UK, Independent reported.

"That is very sad," Mr Trump said about the incident, adding that it was "something that should never, ever happen and we're taking it very seriously". 

The UK, Germany, France, and now the US have jointly called on Russia to explain the military-grade novichok nerve toxin attack on Sergei Skripal and his daughter Yulia in Salisbury. The pair remains in critical condition.