Buses likely carrying expelled American diplomats departed from the U.S. Embassy in Moscow on Thursday.
People were spotted leaving the residences at the embassy compound, placing luggage on trucks.
Russia last week ordered 60 American diplomats to leave the country by Thursday in retaliation for the United States expelling the same number of Russians.
The moves were part of a deepening dispute over the nerve-agent poisoning in Britain of a Russian former double-agent and his daughter.
Britain alleges Russian involvement, which Moscow vehemently denies.
Britain the United States and a host of other countries have expelled more than 150 Russian diplomats in the fallout over the attack in Britain.