A group linked to the hacker network Anonymous on Saturday said it had attacked the Swedish government's website, bringing it down for periods of time by overloading it with traffic.
CyberForce used Twitter to claim responsibility, saying "We have succeeded in the attack against the government."
It also indicated it may launch more attacks at around midnight (2300 GMT) Saturday, saying "this op starts at 24.00," but it was not immediately clear who the targets for those attacks may be.
The group said it had used a denial of service attack against the government, which essentially swamps a website with false users.
Government spokesman Jacob Lagercranser confirmed the website — used by all departments of Sweden's government — had experienced some problems, but he declined to give further details, saying the government never comments on security issues.
"Periodically we've experienced some problems in getting in on it. We're working on the problems," he said. The site was up and running again later Saturday.
CyberForce describes itself as part of the hacking collective Anonymous, which drew international attention by hacking onto a private conference call by the FBI and Britain's Scotland Yard, then publishing the roughly 15-minute-long recording of the call on the Internet on Friday.
In the past week, Saboteurs have stolen passwords and sensitive information on tipsters while hacking into the websites of several law enforcement agencies worldwide.
The alleged Swedish attack, launched at around midday local time, coincided with protests in Stockholm and Sweden's second largest city Goteborg, demonstrating against the Anti-Counterfeiting Trade Agreement, or ACTA.
In a tweet, CyberForce suggested the attack could be linked to those protests, saying "we're not protesting on the (street), we're protesting on the Internet."
ACTA is a far-reaching agreement that aims to harmonize international standards on protecting the rights of those who produce music, movies, pharmaceuticals, fashion, and a range of other products that often fall victim to intellectual property theft.
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