Tens of thousands protested against Iraqi Prime Minister Nuri al-Maliki in Sunni areas Friday as data showed a rise in attacks, indicating militants are seeking to capitalise on a prolonged political crisis.

The rallies came a week after eight demonstrators were shot dead by soldiers in the western town of Fallujah, dramatically raising tensions in what analysts have said is a markedly more dangerous stage of Iraq's perennial instability.

Insurgents have sought to ride the wave of anger against Maliki and his government, with Al-Qaeda's front group in Iraq issuing an audio message on Thursday calling on Sunnis to take up arms.

Protesters gathered in Baghdad and several cities and towns in the mostly Sunni north and west, complaining of the alleged targeting of their minority by the Shiite-led authorities.

"We want the fall of the regime -- no negotiations," proclaimed one banner in Fallujah, where thousands of demonstrators gathered.

"I will continue to protest, even if I am the one one left," said Osama Nayif, one of the Fallujah protesters. The 25-year-old was among 59 people who were wounded in Fallujah last week.

In Ramadi, capital of Anbar province which surrounds Fallujah, many protesters held up flags dating back to the rule of now-executed dictator Saddam Hussein.

"I call for the Arab League and the United Nations to protect the demonstrators and to pressure the Iraqi government to listen to the people's demands," said protester Abdulrahman al-Ghawi.

And in Adhamiyah, a mostly Sunni neighbourhood of north Baghdad, several hundred demonstrators resumed their weekly protest under heavy security measures at the Abu Hanifa mosque, calling for the release of prisoners they say are being wrongfully held.

The demonstrations were the latest in a wave of rallies that have continued largely uninterrupted since late December, sparked by the arrest of a group of guards of Finance Minister Rafa al-Essawi, a senior Sunni leader.

Maliki faces myriad problems, including vocal opposition from many of his erstwhile government partners less than three months before key provincial elections.

Iraqi authorities have taken several steps aimed at curbing the protests.

Officials claim to have released nearly 900 prisoners, and have pledged to raise the salaries of anti-Qaeda militiamen, while a top minister has publicly apologised for holding detainees without charge for prolonged periods.

Crispin Hawes, Middle East and North Africa director at the Eurasia Group consulting firm, warned that Maliki was trying to use a one-size-fits-all approach to solve the current crisis.

Hawes noted that Maliki's comfort with his strategy meant he would find it more difficult "to adapt to more dangerous situations. ... And I think that may be where he is now."

The latest rallies come a day after Al-Qaeda's front group in Iraq released an audio message urging Sunnis to take up arms against the Shiite-led government.

"You have two options," a voice in the audio message, purportedly that of Islamic State of Iraq (ISI) spokesman Abu Mohammed al-Adnani, said. "You can kneel to them (the government), and this is impossible, or carry weapons and you will be the superior."

Figures compiled by AFP showed that January was Iraq's deadliest month since September, with attacks nationwide killing 246 people, implying that insurgents are seeking to capitalise on the political instability.

The ISI claimed much of last month's unrest, and regularly staged deadly attacks in the past in a bid to destabilise the government and push Iraq back towards the sectarian bloodshed that blighted it from 2005 to 2008.