Vladimir Putin has said clashes between Russian and Ukrainian forces are inevitable and it is just a question of time.
In a television address, the Russian president said he had authorised a “specialised military operation” in Ukraine’s Donbas region.
He said the aim was to protect people, but circumstances demanded decisive action from Russia.
He claimed the actions were in self defence and that further NATO expansion and its use of Ukraine’s territory was unacceptable.
Mr Putin said the response would be instant if anyone tries to take on Russia and in comments directed towards the Ukrainian military he said your fathers and grandfathers did not fight so you could help “neo-Nazis”.