SAN FRANCISCO - Elon Musk's X was inaccessible on Monday morning for thousands of users, including many in the United States.

After about eight hours of outage, Musk posted that the platform faced a "massive cyberattack."

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"There was (still is) a massive cyberattack against X. We get attacked every day, but this was done with a lot of resources," he wrote on X.

According to Downdetector, a website that tracks users' reports of online outages, X went down for some users around 5:30 am Eastern Time, with more than 20,000 users reporting outages.

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Though these outages seemed to have resolved after about an hour, the outages returned around 9:30 am Eastern Time, with more than 40,000 users reporting issues. Some users were able to access X intermittently, but the issues continued past 1:30 pm Eastern Time.