Elon Musk says that multiple outages on his social media site X were caused by cyberattacks that originated in Ukraine, despite a hacker group already taking responsibility for the operation.

Mr. Musk has been highly critical of the Ukrainian government and President Zelensky since President Trump announced he would not provide support for the country as his administration tries to work out a peace agreement with the Russians. 

The outages at X began early Monday morning, according to the website DownDetector, which tracks website outages. The first report came just after 5:30 a.m. on Monday, with more than 20,000 people reporting problems with the site over the course of just half an hour. At around 10 a.m., more than 40,000 people had reported the site being down. In total, more than 100,000 people reported to DownDetector that the social media site was not working on Monday. 

“We’re not sure exactly what happened, but there was a massive cyberattack to try to bring down the X system with the I.P. addresses originating in the Ukraine area,” Mr. Musk said in an interview with Fox Business on Monday afternoon. 

A decentralized hacker group called Dark Storm has already taken responsibility for the Distributed Denial of Service attack on the social media site, according to a post on the messaging app Telegram. 

“Twitter has been taken offline by the Dark Storm Team,” an individual wrote in the Telegram chat. 

Monday was a rough day for the world’s richest man, not just due to the cyberattack against his prized social media site, but also because of a major sell-off of his car company’s stock. Tesla shares fell by more than 15 percent on Monday alone, and are currently down more than 36 percent in the last month.