Twitter, the New York Times and the Huffington Post are among ten websites believed to have been hacked by the Syrian Electronic Army.
The NYT's website went offline for the second time this month at about 7pm on Tuesday due to a "malicious attack" by hackers.
The publication denied a cyber attack was responsible for an earlier outage in August 2013, which it blamed on a faulty service update.
However, hackers of the Syrian Electronic Army, which supports President Bashar al-Assad, are suspected to be behind the latest incident, which saw the NYT website partially offline for three hours.
The publication stated on Facebook: "Our initial assessment is that this is most likely the result of a malicious external attack."
Meanwhile, the company's CTO Mark Frons warned staff to be careful while sending e-mails till the issue was rectified.
In January, hackers were successful in stealing passwords of 53 employees of the New York Times, while Chinese hackers have been accused of targeting the NYT and Wall Street Journal for months.
The Huffington Post has also confirmed a recent attack and said there was a "minimal disruption of service", while the army also claimed to be behind a hack on twitter's administrative contact information on Tuesday.
According to security researchers, digital evidence shows that the hacked sites were all registered through a company in Australia.
The hacking army hit Reuters in July, when its Twitter account was made to tweet pro-Assad cartoons.
Earlier this month news websites including the Washington Post, CNN and Time were reportedly hacked by the Syrian Electronic Army, which redirected readers to their website.
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