Russia said on Wednesday it was ordering US Embassy staff who have been in Moscow for more than three years to fly home by Jan. 31, a retaliatory move for a US decision to limit the terms of Russian diplomats.

The step, the latest in an escalating diplomatic row, comes after Russia's ambassador to the United States said last week that 27 Russian diplomats and their families were being expelled from the United States and would leave on Jan. 30.

Washington says the diplomats were not expelled but had been in the country for longer than a new three-year limit.