Two Iraqi Sunni Muslim candidates were killed less than a week before local elections that are considered a major test of the country's political stability after U.S. troops left more than a year ago.

The election on Saturday to select provincial council members will measure Prime Minister Nuri al-Maliki's political muscle against Shi'ite and Sunni rivals before the parliamentary election in 2014.

Violence and suicide bombings have surged since the start of the year with a local al-Qaeda wing promising a campaign to stoke sectarian confrontation among Shi'ites, Sunni Muslims and ethnic Kurds.

No group claimed responsibility for the weekend attacks, but the two candidates killed since late Saturday night were moderate Sunnis campaigning in mostly Sunni areas where Islamist insurgents target political rivals.

Police said gunmen in Baiji town, 180 km (112 miles) north of Baghdad, killed Hatem al-Dulaimi, who was connected to the al-Ensaf Front group headed by Sunni politician Mishaan al-Jubouri. Jubouri once ran a small block in parliament.

"My cousin was secular, and his speech was moderate," said Dulaimi's cousin Ali Sabah. "I think those who killed him were the political groups with ties to the armed groups which operate in this area."

Hours later on Sunday morning, a roadside bomb killed Najim al-Harbi, with two of his brothers and a bodyguard in Diyala province, police said. Harbi had ties to Deputy Prime Minister Saleh al-Mutlaq, a Sunni who has edged closer to Maliki since his Sunni-backed Iraqiya block splintered.

Another Sunni candidate escaped a separate roadside bomb in Balad Ruz, 90 km (55 miles) northeast of the capital on Sunday, authorities said.

SUNNI DIVISIONS

Ten years after the U.S.-led invasion, Sunni ranks are deeply divided over how to manage a power-sharing agreement with Maliki. Some moderate leaders work with the government but others see the Shi'ite premier as an authoritarian.

Thousands of Sunni Muslims have protested since December in western provinces at what they see as their marginalisation since the fall of Saddam Hussein and the rise of the country's Shi'ite majority to power since the 2003 invasion.

Many Iraqi Sunnis feel they have been sidelined from power-sharing and unfairly targeted by security forces. Maliki has offered concessions on reform of tough anti-terrorism laws and released prisoners. But Sunni protests continue.

Washington has weighed into the election process, warning of the risks of disenfranchising Sunni voters after Maliki's cabinet postponed voting in two majority Sunni provinces because local officials said security could not be provided there.

Even in Maliki's Shi'ite coalition there are political splinters. The Sadrist block, led by anti-U.S. cleric Moqtada al-Sadr, has threatened to break Maliki's coalition, even backing an attempt at a vote of no-confidence against him.

More than 8,000 candidates are running for nearly 450 seats, except in the three provinces administered by the country's autonomous Kurdistan region and in the disputed city of Kirkuk. Election officials may hold the postponed vote in Anbar and Nineveh provinces a month later.