* Thousands of protesters out since late December
* Many see Maliki's gov't biased against Sunnis
* Tensions high a week after soldiers open fire
By Kamal Naama
FALLUJA, Iraq, Feb 1 (Reuters) - Chanting "No" to Iraqi Prime Minister Nuri al-Maliki, tens of thousands of Sunni Muslims protested after Friday prayers in huge rallies against the Shi'ite premier that are raising the spectre of renewed sectarian unrest.
Sunni Muslim outrage erupted in late December over what protesters see as abuses and discrimination against their minority sect since the fall of Saddam Hussein and the rise of the country's Shi'ite majority.
Waving the old three-star Iraqi flag from Saddam's era, Sunni clerics, tribal sheikhs and young protesters called for reform of anti-terrorism laws they say security forces abuse to target Sunnis and unfairly detain prisoners.
Wary of Islamists inciting Sunni anger, Maliki has offered concessions, and freed hundreds of prisoners. But Sunni protesters have grown more defiant after soldiers opened fire at a Falluja city rally, killing five people a week ago.
"We will never forget what the army did to us, not only last Friday, but all of their behaviour has been sectarian against us," Omar Al-Jumaili, 51, in Falluja city. "Our new demand; the Iraqi army should leave this area."
Sunni ranks are already split among moderates and hardline Islamists who are threatening Iraq's unity with a more radical demand for an autonomous Sunni fiefdom in western Iraq along the border with Syria, Saudi Arabia and Jordan.
The protests are evolving in the most serious test yet for Maliki and his fragile government that splits posts among Shi'ite, Sunni and ethnic Kurds, who were already deadlocked over how to share power for more than a year.
Iraq's al Qaeda affiliate, Islamic State of Iraq, still active after years of losses against American and Iraqi soldiers, has also urged Sunni protesters to take up arms though moderate leaders reject the incitement to violence.
Al Qaeda claimed a suicide bombing that killed a Falluja lawmaker last month, and Sunni Islamist insurgents continue to hit Shi'ite targets in an attempt to spark inter-communal confrontation between the sects.
A year after the last American troops pulled out, sectarian tensions are still raw in the OPEC country, where Shi'ite on Sunni violence killed tens of thousands of people just a few years after the 2003 U.S.-led invasion.
Maliki has appointed a senior Shi'ite figure to talk to demonstrators about demands such as an amnesty law and easing of so-called de-Baathification campaign against former members of Saddam's outlawed Baath party.
Iraq's vice premier Saleh al-Mutlaq, a Sunni, said a meeting on Friday with Maliki's Shi'ite National Alliance coalition and Sunni-backed Iraqiya had been positive on proposed reforms.
"We can say there was a progress in this meeting, which may be hasn't happened in the previous ones," he said.
The Sunni unrest broke out just as Baghdad is struggling also with a dispute with the autonomous Kurdistan region over oil and land rights. That has complicated Maliki's attempts to build alliances with Sunni and Kurdish leaders.
Sunni unrest and renewed violence in Iraq are also compounding fears war in neighbouring Syria - where Sunni rebels are battling President Bashar al-Assad, an ally of Shi'ite Iran - will fracture Iraq's own sectarian and ethnic balance. (Additional reporting by Raheem Salman; Writing by Patrick Markey; Editing by Jon Hemming)