Ukrainian Border control authorities have formally served notice on Mikheil Saakashvili charging him with illegal entry into Ukraine on Sunday.
The Georgian ex-president and one-time regional governor in Ukraine said he was swept over the border into Ukraine by crowds, angry that the crossing was closed.
He claimed the authorities were heavy-handed.
He said: “It was an extremely irresponsible action. Instead of letting me in, taking my passport, they are not letting me in and suggesting I go through all these procedures. They were afraid to let me into the Ukrainian territory.”
On Sunday there were scuffles at the Ukrainian border between Mr Saakashvili’s supporters and border officials.
Ukrainian Interior Minister Arsen Avakov said Mikheil Saakashvili faced “serious” criminal charges for crossing the border and said it was “an attack on the state’s basic institutions.”
Mr Saakashvili was stripped of his Ukrainian citizenship in July, by President Petro Poroshenko after disagreements about proposed reforms.
He is currently wanted in Georgia on allegations of corruption and abuse of power but claims that the UNHCR recognises him as being “stateless.”