US Secretary of State Antony Blinken said he had seen reports from Moscow of an alleged drone attack by Ukraine on the Kremlin, but he "can’t in any way validate them."
"We simply don't know," Blinken said Wednesday at a Washington Post Live event.
"I would take anything coming out of the Kremlin with a very large shaker of salt," he added.
"We'll see what the facts are. And it's really hard to comment or speculate on this without really knowing what the facts are," Blinken added.
Ukraine has denied any knowledge of the alleged drone attack in Moscow.