MOSCOW — Russia on Saturday expelled two American diplomats who it said were working undercover for the CIA, in retaliation for the US expulsion of two Russians.

The expulsions followed a scuffle between a Russian guard and an American diplomat outside the US embassy in Moscow in June. That diplomat is one of the two Americans expelled, Deputy Foreign Minister Sergei Ryabkov said Saturday.

Washington said the guard attacked the diplomat and the State Department on Friday announced that two Russians were expelled last month in response.

Russia alleges that the American tried to rush into the embassy late at night after a spying mission without presenting identification and was tackled by the guard.

The Russian officials were expelled June 17, State Department spokesman John Kirby said. ‘‘The Russian claim that the policeman was protecting the embassy from an unidentified individual is simply untrue,’’ he told reporters.

A video of the scuffle, released earlier this week by state-owned television NTV, shows a man exiting a taxi in an area resembling an embassy entrance and striding toward the doors. The guard bursts out of a sentry box and tackles the man, who is able to crawl through the entrance doors.

The incident was the latest in what the State Department calls harassment and ill treatment of American diplomats working in Russia. Moscow denies those accusations and says the United States is spreading disinformation about Russia.

Ties between Moscow and Washington have sunk to Cold War levels in recent years over Russia’s annexation of Crimea, its support of separatist rebels in eastern Ukraine and its actions in Syria.

The tensions have been on display in Warsaw, where leaders of the 28-nation NATO alliance are holding a summit.

President Obama said last week that the United States will send 1,000 more troops to Poland as part of the plan for NATO to deploy four multinational battalions to the alliance’s Russian flank. Others battalions will go to Estonia, Latvia, and Lithuania.

In Lithuania, Germany will be the framework nation for a battalion that will include troops from seven NATO member nations. Britain will lead a battalion in Estonia with 500 of its own troops but also a company each from France and Denmark. Canada will head a battalion based in Latvia.

Meanwhile, Russian and US cooperation is continuing unabated in space.

Three astronauts from the United States, Russia, and Japan boarded the International Space Station on Saturday after a two-day journey aboard a Russian Soyuz space capsule.

The capsule docked smoothly with the space station Saturday at 254 miles above the Earth. Russia’s space agency Roscosmos said the crew entered the station about two hours later.

Russian Anatoly Ivanishin, NASA’s Kathleen Rubins and Takuya Onishi of the Japanese space agency JAXA are beginning a four-month stay on the orbiting space laboratory.

They joined American Jeff Williams and Russians Oleg Skripochka and Alexey Ovchinin, who have been aboard since mid-March.

The capsule blasted off from Russia’s manned space complex in Baikonur, Kazakhstan, on Thursday.