A number of Dutch government and other websites were taken offline on Tuesday by a cyber attack, broadcaster Nos says on Wednesday.

The national government website regering.nl, phone company Telfort and shock blog Geenstijl could not be reached from around 10.00 hours until the evening because of the so-called DDoS attack.

A DDoS or denial-of-service attack involves bombarding a site with data traffic which makes it extremely difficult to reach.

Government websites were also put offline by a DDoS attak in May 2013 but that only lasted four hours.

Labour MPs have demanded an explanation for the most recent attack, which left ministry websites effectively closed. It is ‘astonishing’ that there is no simple back-up to ensure the government can still be reached online, the party is quoted as saying by website nu.nl.

It is not clear who was behind the attack or what the target actually was, nu.nl says.