Portsmouth City Council has become the latest local authority to be hit by a cyber attack.
The unitary council said it was among those affected by a distributed denial-of-service (DDoS) attack by a group calling itself NoName057(16).
Pro-Russian hackers have claimed responsibility for the attacks, which have also affected Salford and Middlesbrough, among others.
Portsmouth said no council services were affected and that residents’ data was not at risk.
A statement on the authority’s Facebook page said: “We can confirm that the Portsmouth City Council website is undergoing a cyber attack, which means you will experience issues when trying to use the site.
“Portsmouth is one of a number of local authorities across the UK to be affected by a distributed denial-of-service (DDoS) attack by a group named NoName057(16).
“No council services are affected by the attack, and user and residents’ data are not at risk, however, the website may be for an unknown period.
“We’re working to resolve the issue as soon as possible and apologise for any inconvenience caused.”
The council said its teams were still available to answer queries during working hours and residents could access online services and make payments on the MyPortsmouth website.
Other councils have also been hit by cyber attacks this week.
Salford, Bury and Trafford councils confirmed their websites were temporarily affected but said they were now back online.
Middlesbrough Council’s site was taken offline on Wednesday after its IT department identified an issue.
A National Cyber Security Centre (NCSC) spokesperson said the organisation provided guidance to affected councils.
They told the Local Democracy Reporting Service: “Whilst DDoS attacks are relatively low in sophistication and impact, they can cause disruption by preventing legitimate users from accessing online services.”