Russia has said it will consider the Salisbury nerve agent attack a murder attempt on one of its citizens if the UK cannot prove that its intelligence services did not carry out the attack.
The Russian Foreign Ministry claimed this morning that British spies may have been involved in the attempted murder of Sergei Skripal and his daughter earlier this month.
Britain has insisted the Russian state was behind the attack - with Russian diplomats being expelled from the US, Canada, Australia and countries across Europe in response.
Moscow has continued to deny any involvement - pledging a mirror-like response to the expulsions of its diplomatic corps.
A total of 25 countries have expelled more than 130 diplomats.
The Kremlin on Wednesday said it will "definitely retaliate" against the West over the expulsions.
in a statement it said an "analysis of all the circumstances" surrounding the attack had led it to consider the "possible involvement" of the British intelligence services in the attack.
“If convincing evidence to the contrary is not presented to the Russian side we will consider that we are dealing with an attempt on the lives of our citizens as a result of a massive political provocation,” it said.
An Irish diplomat is now expected to be expelled from Russia in response to the yesterday's Government's decision to send one Russian representative home in solidarity with the UK.
On Newstalk Breakfast this morning, Russia Today journalist Bryan McDonald said the retaliatory expulsion will happen in the next few days.
"What the Russians see as the British over-reaction or wrongful reaction contributed to consolidating support amongst Russians who feel their country has been victimised," he said.
A spokesman for Russian President Vladimir Putin has said the leader "remains open" to holding a summit with US President Donald Trump, despite his decision to expel 60 diplomats from the US.
Dmitry Peskov said: "This depends on the American side, but the Russian side remains open."
"Putin is ready and the Russian side is ready for mutually beneficial and mutually trustful relations with all countries including the US to the extent that our opponents or partners are ready for this."
Former double agent Sergei Skipral and his daughter Yulia remain under heavy sedation in hospital over three weeks after being found unconscious on a bench in Salisbury, southern England.
Their condition is described as critical but stable.