Tough EU sanctions against Russia may come into force immediately after they are announced by EU ambassadors on Tuesday, Finnish Prime Minister Alexander Stubb has said.

He said that restrictive measures against Russia would affect the financial services industry, armaments, imports and exports of dual-use goods, and sensitive technologies.

"The sanctions will take effect immediately upon approval," he told the Finnish television and radio broadcasting portal Yle.

He said that the sanctions were designed for a year, but after six months the situation would be reviewed again.