“This Friday we will do the biggest thing we have ever done. We will not say what we will do yet,” an artificial sounding voice proclaimed in the clip, which claims ties to Anonymous and was broadcast on YouTube.

The latest threat comes after a slew of DDOS attacks carried out on Swedish agencies.

The National Board of Health and Welfare (Socialstyrelsen) website was down on Tuesday evening, and after a threat from hacktivists, claiming to be part of the Anonymous network, the Swedish Riksbank site went down late on Wednesday evening.

Throughout Wednesday, many university sites around the world were also hacked, including Sweden’s Uppsala and Lund universities.

The Riksdag website and that of the Swedish government were also rendered inaccessible on Wednesday night.

According to the clips posted on YouTube, the attacks are said to be in retaliation against Monday’s raid by Swedish police on web hosts PRQ, previously hosting both The Pirate Bay and WikiLeaks.

However, according to one expert on IT crime, it is impossible to say whether the last three days’ attacks have actually been carried out by Anonymous, or if the alleged hacktivist network even exists:

“No one in the world knows what Anonymous is,” said Anders Ahlqvist of the National Police Board (Rikspolisstyrelsen) to daily Svenska Dagbladet (SvD).