The opposition New Generation party had called for demonstrations in Sulaimaniyah and other cities in the country's north in protest against deteriorating living conditions, alleged corruption and authoritarian practices by the regional government.

Dozens of police vehicles were deployed to the centre of Sulaimaniyah, and security forces fired tear gas and rubber-coated bullets once several hundred protesters had gathered, an AFP correspondent reported.

Security forces stopped journalists from taking images of the crackdown.

Six New Generation lawmakers in the federal parliament in Baghdad who were preparing to join the protests, and another from the regional parliament, were taken in for questioning for a few hours, the bloc's chief Srwa Abdulwahid told AFP. They were all later released, she said.

Abdulwahid posted photographs on Twitter of some 30 activists she said had been arrested in recent days.

Human rights associations regularly criticise Iraqi Kurdish authorities for carrying out arbitrary arrests, suppressing protests and attacking press freedoms.

Keen on projecting an image as a relative haven of stability and tolerance in war-battered Iraq, the autonomous region has long been dominated by the Kurdistan Democratic Party (KDP), led by the Barzani family, and the rival Patriotic Union of Kurdistan (PUK), headed by the Talabani clan.

The crackdown in the Kurdistan region comes as supporters of powerful Shiite Muslim leader Moqtada Sadr have been holding a sit-in in the gardens around parliament in Baghdad's normally secure Green Zone, home to government and diplomatic buildings.

The cleric's supporters occupied the legislature last Saturday and remained inside the building for several days, protesting against a rival Shiite bloc's pick for the premiership.