In a message posted to the Telegram messaging app on Sunday, IS spokesman Abu Hassan al-Muhajir called on Sunni Iraqis to boycott the May 12 polls, the first since Iraqi Prime Minister Haider al-Abadi declared victory over the jihadists in December.

"Oh Sunnis... we know that the government of Rafida (a pejorative Arabic term for Shiites) is on the verge of what they call elections," he said.

"Our judgement will apply to those who call for them and participate in them... The voting centres and those in them are targets for our swords, so stay away from them and do not walk nearby."

Sunni extremist groups have long targeted Shiites, a majority in Iraq.

Jihadist groups in Iraq have targeted every election since the 2003 US-led invasion that deposed Saddam Hussein and paved the way for Shiites to dominate every government since.