About 150 US troops from the Florida National Guard who are in Ukraine to help train Ukrainian forces are leaving the country as the threat of a Russian invasion increases, two US officials told Reuters.

According to the report, the officials said the decision was made after the State Department ordered some US embassy staff in Ukraine to leave.

The officials said it was not yet clear where the troops would be repositioned.

It was not immediately clear what would happen with the small number of US special operations forces in the country, said one of the officials.

Australia, New Zealand, Germany and the Netherlands on Saturday joined countries urging their citizens to leave Ukraine.

Moscow has repeatedly disputed Washington's version of events, saying it has massed more than 100,000 troops near the Ukrainian border to maintain its own security against aggression by NATO allies.

(With input from agencies)