Iraq ( Troops shot and killed four people during a protest ) Falluja

FALLUJA, Iraq (Reuters) - Iraqi troops shot dead at least four people during clashes with Sunni Muslim protesters in Falluja on Friday in escalating unrest against Shi'ite Prime Minister Nuri al-Maliki.

A Reuters witness said troops initially fired in the air to disperse crowds, but then he saw some soldiers fire towards protesters who had approached their military vehicles and set one of them on fire.

Thousands of Sunnis have taken to the streets to protest against mistreatment of their minority sect since late December, increasing worries that Iraq could slide back into widespread sectarian confrontation.

Friday's violence complicates Maliki's attempts to end the protests, where demands range from amendment of terrorism laws that many Sunnis feel single them out to more radical calls for the Shi'ite leader to step down.

After thousands gathered for Friday prayers in Falluja, a mostly Sunni city 50 km (30 miles) north of the capital, clashes broke out when troops arrested three protesters and others tried to block a major highway, officials said.

"A final count shows we have six people killed and 52 wounded," a hospital source told Reuters. He said at least four had died from gunshot wounds, but it was not clear how the other two people had died.

A local television channel showed demonstrators approaching the army vehicles and throwing stones and water bottles while troops tried to keep them away by firing in the air. But images also showed one soldier aiming his rifle at demonstrators.

"I was trying to see the burned vehicle when the army started to drive the demonstrators away. When that did not work the soldiers opened fire at the people," said Aziz Nazal, a cameraman, who was wounded in his hand.

A year after the last American troops left Iraq, sectarian tensions are still raw in Iraq, where many lived through Shi'ite-against-Sunni bloodletting that killed tens of thousands a few years after the 2003 U.S.-led invasion.

Since the fall of the Sunni dictator Saddam Hussein a decade ago, many Iraqi Sunnis feel they have been sidelined by the Shi'ite leadership and believe Maliki is amassing power at their community's expense.