Russia has expelled a first secretary at the Canadian embassy in Moscow in what it said was a response to Canada's earlier expulsion of a Russian assistant military attache, Russian news agencies quoted a foreign ministry source as saying.

A demonstrator takes part in a protest against the referendum in Ukraine's Crimea region, outside the Russian embassy in Ottawa, in March. Credit: Reuters

"On April 22, the Canadian diplomatic mission in Moscow was informed of the expulsion from the Russian Federation, within 14 days, of the first secretary of the embassy," Itar-Tass quoted a ministry source as saying.