MOSCOW — Russia’s military acknowledged on Tuesday that it had conducted a test of an antisatellite weapon that obliterated a target in orbit, sending a vast cloud of debris zipping around Earth and forcing astronauts on the International Space Station to seek shelter.
The announcement followed a day of silence in Moscow about the sophisticated weapon test, coming amid already heightened military tensions between the United States and Russia.
Earlier on Tuesday, a Russian member of Parliament had denied any test took place, though some of the fragments had loomed near enough to the International Space Station that astronauts closed hatches and took shelter.
The Russian weapon, identified in Russian news reports as possibly an S-500 Prometey missile, blew up a long-defunct Soviet signal intelligence satellite that had been launched in 1982 and was orbiting silently for years.
The blast created more than 1,500 pieces of trackable debris and is likely to eventually generate hundreds of thousands of smaller pieces, according to the U.S. State Department, which was sharply critical of the test for posing dangers to satellites and crewed spaceships.
Secretary of State Antony J. Blinken, in a statement on Monday, sharply criticized the test as “recklessly conducted.”
The U.S. Space Command said the debris is likely to remain in orbit for years or even decades, adding to a vast array of space junk. A few days before the Russian test, the space station had to dodge debris from a 2007 Chinese weapons test.
“The Ministry of Defense of Russia successfully completed a test,” the ministry said in a statement on Tuesday, in the country’s first official acknowledgment. “The result was the destruction of an inactive Russian space apparatus.”
The debris cloud, the statement said, posed no risk to the International Space Station, other crewed spaceships or satellites, it said.
Earlier on Tuesday, the deputy chairman of the Russian Parliament’s committee on defense, Yuri Shvytkin, had denied any test took place. “The fantasy of the State Department knows no bounds,” Mr. Shvytkin said, the Interfax news agency reported. “Russia is not militarizing space.”
There was no explanation for the contradictory statements or indication that Russia’s two cosmonauts on the International Space Station had received advance warning.
Along with two Americans and one German astronaut on board, the Russians took shelter for about two hours on spaceships docked to the station that could return them to earth if needed.
NASA’s administrator, Bill Nelson, said he had “no reason to believe” Russia’s human spaceflight program was aware of the military missile test. He noted the debris cloud also endangered three astronauts now aboard China’s Tiangong space station.
The international fallout from the episode spread Tuesday. In a post on Twitter, Florence Parly, France’s defense minister, did not mention Russia by name but criticized “vandals” for polluting outer space.
“Space is a common good, that of the 7.7 billion inhabitants of our planet,” she said. “Space vandals have an overwhelming responsibility by generating debris that pollutes and puts our astronauts and satellites in danger.”
Ms. Parly said the European Union was cleareyed that space was a new “territory for conflict.”
Managing space junk has been a looming problem for years. The Russian test added to an already vast swarm of junk in orbit, including old satellites, parts of rockets and debris from earlier antisatellite weapon tests by China, India and the United States.
The surprise Russian weapons test added to already mounting military tensions throughout Eastern Europe this fall as Belarus has driven migrants toward the Polish border, the United States is conducting a naval drill in the Black Sea and Russia has massed troops along the Ukrainian border.
Aurelien Breeden contributed reporting from Paris.