Updated

The Australian government has summoned the Russian ambassador to explain his country's actions in Ukraine.

Foreign Minister Julie Bishop said the secretary of her department, Peter Varghese, will meet with Ambassador Vladimir Morozov on Monday.

Bishop told Australian Broadcasting Corp. radio: "We'll express our concerns officially, directly through him and also seek to ascertain exactly what the Russian government thinks it's doing."

Ukraine put its military on high alert Sunday and appealed for international help to avoid what it fears is the possibility of a wider invasion by Russia.

A day after Russia took control of the Crimean peninsula without firing a shot, fears grew in the Ukrainian capital and beyond that Russia might seek to expand its control by seizing other parts of eastern Ukraine.