According to Snopes, The New York Times has stated that they verified two videos of what appeared to be drones flying and exploding by the Kremlin State, but did not confirm who was behind the attack.
So far Russia has been the only one to say the source of the drones, blaming Ukraine, but Ukraine is denying this claim and says their fight is only in Ukraine.
No independent news source has been able to identify the source of the attack. The United States and other nations are still trying to verify the source of the attack, along with it’s credibility.
Snopes has deemed there is not enough information currently available.
“Because both sides of the war offered differing accounts of who was responsible for the drone attacks, and no independent reporting had confirmed the sources, we have rated this claim as "Research in Progress." We will update this story when we learn more” (Snopes).
https://www.snopes.com/fact-check/ukraine-attack-kremlin-in-russia-with-drone/
The New York Times has stated, “If the explosions were indeed a drone attack, the penetration of central Moscow’s air defenses would represent the latest embarrassing failure by a Russian military that has struggled throughout the 14-month war” (The New York Times).
https://www.nytimes.com/live/2023/05/03/world/russia-ukraine-kremlin-drone-news