Twitter Inc TWTR.N was down for thousands of users on Tuesday, according to outage tracking website Downdetector.com.
Downdetector, which tracks outages by collating status reports from a number of sources, showed more than 15,000 outage reports.
"We're looking into this now, will get back to you ASAP," Twitter told Reuters in an emailed statement.
The social media platform, which is in a legal tussle with Tesla TSLA.O boss Elon Musk over his $44 billion takeover deal, faced a nearly three-hour outage in July, with the company saying it had some trouble with its internal systems that impacted many globally.
Notorious for outages in its early years, Twitter was known for using its popular "Fail Whale" illustration, which showed a beluga whale being lifted by birds, during such incidents.
Twitter had suffered another widespread outage in February that it blamed on a software glitch.