* Tens of thousands protest in Falluja, Ramadi, Mosul, Samarra
* Sunnis accuse PM of marginalising them, being influenced by Iran
* Protests fuel concerns Syria could further destabilise Iraq
By Kamal Naama and Raheem Salman
RAMADI, Iraq, Dec 28 (Reuters) - Thousands of protesters from Iraq's Sunni Muslim minority poured onto the streets after Friday prayers in a show of force against Shi'ite Prime Minister Nuri al-Maliki, keeping up a week-long blockade of a major highway.
Around 60,000 people blocked the main road through Falluja, 50 km (30 miles) west of the capital, setting fire to the flag of Shi'ite Iran and shouting "out, out Iran! Baghdad stays free" and "Maliki you coward, don't take your advice from Iran".
Many Sunnis, whose community dominated Iraq until the fall of Saddam Hussein in 2003, accuse Maliki of refusing to share power and of being under the sway of its non-Arab neighbour.
"We will not leave this place until all our demands are fulfilled, including the toppling of the Maliki government," said 31-year-old Omar al-Dahal at a protest in Ramadi, where more than 100,000 protesters blocked the same highway as it leads to neighbouring Syria and Jordan.
Activists' demands include an end to the marginalisation of Sunnis, the abolition of anti-terrorism laws they say are used to target them, and the release of detainees.
Protests flared last week in Anbar province, the Sunni stronghold in western Iraq where demonstrators have mounted the blockades, after troops loyal to Maliki, who is from the Shi'ite majority, detained bodyguards of his finance minister, a Sunni.
Demonstrations were also held in the northern city of Mosul and in Samarra, where protesters chanted "the people want to bring down the regime", echoing the slogan used in popular revolts that ousted leaders in Tunisia, Egypt, Libya and Yemen.
The protests are likely to add to concerns the civil war in neighbouring Syria, where majority Sunnis are fighting to topple a ruler backed by Shi'ite Iran, will drive Iraq back to the sectarian slaughter of 2005-7.
Militants linked to al Qaeda appear to be joining the ranks of Syrian rebels across the border and regrouping in Anbar, which was almost entirely controlled by militants at the height of Iraq's insurgency.
Security forces did not move to break up the protests, but prevented people from other provinces from heading to Anbar to join the rallies there.
Speaking at a "reconciliation" conference broadcast on television, Maliki called for dialogue.
"It is not acceptable to express something by blocking roads, inciting sedition and sectarianism, killing, or blowing the trumpet of war and dividing Iraq," he said.
A masked protester who refused to give his name recalled the role of Anbar's tribes, first in fighting U.S. troops before allying with them to drive militants out - turning on fellow Sunni al Qaeda because of its indiscriminate use of violence.
"Just as we terrified the Americans with this mask, and kicked al Qaeda out, we will terrify the government with it," he said.
Highlighting the increasingly regional dimension, protesters in Falluja raised pictures of Turkish Prime Minister Tayyip Erdogan, who has lined up against Syrian President Bashar al-Assad and has sparred increasingly often with Maliki.
In Iraq's Shi'ite south, a small anti-Erdogan protest was held in the holy city of Najaf, 160 km (100 miles) from Baghdad.
Sunni complaints against Maliki grew louder a week ago following the arrest of Finance Minister Rafaie al-Esawi's bodyguards hours after Iraqi President Jalal Talabani, a Kurd seen as a steadying influence, was flown abroad for medical care.
For many, that was reminiscent of a move to arrest Sunni Vice President Tareq al-Hashemi a year ago, just when U.S. troops had withdrawn. Hashemi fled into exile and was subsequently sentenced to death in absentia.
Maliki has sought to divide his rivals and strengthen alliances in Iraq's complex political landscape before provincial elections next year and a parliamentary vote in 2014.
A face-off between the Iraqi army and Kurdish forces over disputed oilfields in the north has been seen as a possible way of rallying Sunni Arab support behind the prime minister.