Mikheil Saakashvili, the former Georgian president, has resigned as governor of Ukraine's Odessa region, expressing fury at rampant corruption.

He accused Ukrainian President Petro Poroshenko of backing corrupt officials who, he said, were undermining his reform efforts in Odessa.

"In Odessa region the president is personally supporting two clans," he said - clans which he described as criminal and corrupt.

Mr Saakashvili also criticised the huge wealth of some Ukrainian politicians.

"This is going on quite openly. Odessa region is being handed over not only to corrupt people, but also to enemies of Ukraine," he said.

"I'm sick and tired of all this. So in this situation I decided to resign and start a new phase of struggle."

He said "they declare brazenly that they have billions in cash alone, and on top of that they get state aid - from those very pensioners who collect their last kopecks with shaking hands to avoid dying of hunger".

Mr Saakashvili did not specify what role he would take up next.