Twitter was hacked over the weekend, resulting in the passwords of up to 250,000 user accounts being exposed.
Twitter said in a blog post that the passwords were encrypted and that it had already reset them as a "precautionary measure," and that it was in the process of notifying affected users.
There are growing fears that the Government of China sponsors hackers who work to discover not only the trade secrets of Western companies, but also discover details of critical journalists, Chinese dissidents, and delve into national defence and infrastructure systems.
Beijing spokesmen deny endorsing any computer hacking but companies falling victims to serious attacks repeatedly say they appear to originate in China.
In recent days American newspapers The New York Times, The Wall Street Journal and The Washington Post have also revealed that they have been the targets of sophisticated ‘cyber-attacks’.
"This attack was not the work of amateurs, and we do not believe it was an isolated incident," Twitter said. "The attackers were extremely sophisticated, and we believe other companies and organizations have also been recently similarly attacked."
Twitter did not specifically link the attacks to China in the blog post, in contrast to the New York Times and the Wall Street Journal, which both said the hackers originated in China.
Twitter has 200 million active monthly users, said it was working with government and federal law enforcement officials to track down the attackers.
Twitter could not speculate on the origin of the attacks as its investigation was ongoing, said spokesman Jim Prosser. "There is no evidence right now that would indicate that passwords were compromised," said Prosser.
The attack is not the first time that hackers have breached Twitter's systems and gained access to Twitter user information. Twitter signed a consent decree with the Federal Trade Commission in 2010, subjecting the company to 10 years of independent privacy reviews, for failing to safeguard users' personal information.