Hacking group Lulz Security claims to has taken offline the website of the UK Serious Organised Crime agency (Soca).
Www.soca.gov.uk was unavailable for a time on Monday afternoon and appeared to be working only intermittently by the evening.
With no immediate comment from Soca, LulzSec tweeted: “Tango down – in the name of #AntiSec”.
The group has been responsible for a number of high-profile web attacks, hitting the CIA and US Senate.
Soca has most likely been the victim of a distributed denial of service (DDoS) attack, where a number of computers, under malicious control, overload their target with web requests.
The technique appears to be a favourite of Lulz Security.
Over the weekend, the shadowy group declared that it would begin targeting government systems, calling the campaign Antisec.
In an online posting, Lulzsec set out its agenda: “Top priority is to steal and leak any classified government information, including email spools and documentation. Prime targets are banks and other high-ranking establishments.”