Georgia on Monday accused a senior Ukrainian official of plotting to overthrow the Black Sea nation's government by organising mass unrest, in the latest episode of escalating tensions between the ex-Soviet countries.

Georgia has been accused of cooperating with the Kremlin even though Russian forces have deployed to separatist regions of Abkhazia and South Ossetia since 2008, when Moscow invaded the tiny Caucasus country.

Georgian security services said the deputy chief of Ukraine's military counterintelligence and Georgia's former deputy interior minister, Giorgi Lortkipanidze, was plotting "destabilisation aimed at a violent overthrow of the government."

It said Georgians fighting Russian forces in Ukraine, including a bodyguard of Georgia's jailed ex-president Mikhail Saakashvili, were among the conspirators being trained near Ukraine's border with Poland.

Ukraine has repeatedly called for Georgia to release Saakashvili, who is now a Ukrainian national and a top advisor to Ukrainian President Volodymyr Zelensky.

Kyiv has said that the Georgian authorities are "killing" the ailing politician on Kremlin orders and has demanded his transfer to a clinic abroad.

Georgia in turn has condemned what it said was "an extreme form of escalation in diplomatic relations."

Georgia's security service said anti-government protests "are being planned for October and December, when the European Commission is set to publish its decision on Georgia's EU membership application."

It said the plot "is being carried out with the coordination and funding from a foreign country."

The EU recognised Georgia's "European perspective" last year, but deferred its membership application while granting candidacy to fellow ex-Soviet Ukraine and Moldova.

That has led to mass anti-government protests in Tbilisi, where the government is facing accusations of backsliding on its commitments to democracy and undermining Georgia's EU membership bid.

Earlier in September, EU foreign policy chief Josep Borrell said "there is still quite a bit of work to be done" by Tbilisi to be granted a formal candidate status.