Online hacktivist collective Anonymous has announced OpIran, a new campaign set to coincide with International Workers' Day on 1 May and designed to launch denial of service attacks at Iranian web sites.

In a post on the AnonNews site, the group urged the Iranian people to join an "era of change" sweeping the world.

"We can see that Iran still suffers at the hands of those in power. Your former government has seized control, and tries to silence you," the statement read.

"People of Iran - your rights belong to you. You have the right to free speech and free press, the freedom to assemble and to be safe in your person. You have the right to live free and without fear."

Although no sites are mentioned by name, the group hinted heavily that the denial of service attacks are likely to be launched on the morning of 1 May.

"As International Worker's Day dawns - Anonymous stands with you," the statement concluded.

"We are Anonymous. We are Legion. We do not forgive. We do not forget. Expect Us."

It will not be the first time the group has sought to make a point by disrupting web sites. Most famously it was involved in launching denial of service attacks against firms such as Visa and PayPal which it accused of interfering with the work of whistle-blowing site Wikileaks.

Anonymous has also had long running disputes with Sony, the Egyptian government and radical Christian organisation the Westboro Baptist Church.