A suicide bomber killed the leader of a U.S.-backed Sunni paramilitary group and seven others north of Baghdad Tuesday, the third attack in as many days in a heavily populated Sunni area, a police official said.

The bombing hit a market in the town of Buhriz, a former Saddam Hussein stronghold that was also the scene of an attack on Monday that killed the mayor. It raised concerns that escalating violence toward the Sunni minority could destabilize Iraq as it prepares for national elections early next year.

Violence dropped off dramatically in Iraq after local Sunni tribes — known as Awakening Councils — aligned themselves with U.S. forces. That alliance against Al Qaeda was seen as a key turning point in the war.

The attack in Buhriz, 35 miles north of Baghdad, targeted the local leader of the Awakening Council, said Police Maj. Ghalib al-Kharki, spokesman for police in Diyala province. The bomber followed the leader, Leith Ahmed, into the market before detonating an explosives belt, al-Kharki said. Ahmed was killed instantly, he said. Seven others were killed and seven were wounded.

On Monday, an attack killed the mayor of Buhriz and wounded his two sons. The sons were also members of the Awakening Council, al-Kharki said.

On Sunday, a series of coordinated car bombings killed 19 people in the Anbar provincial capital of Ramadi, once a hotbed of the Sunni-led insurgency.

Meanwhile, lawmakers approved the return of a limited number of British troops to Iraq to help protect the country's southern oil ports — an area where the country is lagging in its ability to provide security.

Iraq's parliament approved the security agreement with Britain months after the military contingent was forced to pull out because a United Nations mandate allowing British troops to legally operate in the country expired.

Under the agreement in parliament Tuesday, about 100 British troops would return for about a year to provide protection to the oil sites and train Iraqi forces. Iraq's president and two vice presidents still must sign off on the agreement.

The deal limits British military operations in Iraq strictly to naval operations at the southern port of Umm Qasr, said Jabir Khalifa Jabir from the parliament's oil and gas committee.

Britain had about 40,000 troops in Iraq following the 2003 U.S.-led invasion, but withdrew almost all their forces earlier this year. A contingent of about 100 to 150 troops who were training Iraq's new navy remained, but those forces were moved to Kuwait when Iraq's parliament went on summer break without agreeing to allow the British to stay.

Lawmakers loyal to anti-U.S. cleric Muqtada al-Sadr walked out in protest during the vote. The group, with about 30 legislators in the 275-member parliament, once staged bloody rebellions against U.S.-led troops, and has strongly objected to any remaining foreign troops.

Iraqi lawmakers also resumed talks Tuesday on the election law — a key piece of legislation that may affect the credibility of the country's parliamentary vote in January.

Iraq's electoral commission gave the assembly until Thursday to approve an election law with new voting guidelines governing the January vote.

U.S. officials have worried that if the election law is not passed in time it could delay the January vote and undermine the country's fragile stability as U.S. forces are withdrawing.

One of the major stumbling blocks has been the issue of whether to have what is referred to as an "open list" in which voters can see the names of the people for which they're voting instead of simply the names of the parties — a "closed list."

Prime Minister Nouri al-Maliki has been a key proponent of the open list, after his success earlier this year in the provincial election, which used the open list system.

Iraq's leading Shiite cleric, Grand Ayatollah Ali al-Sistani, whose opinion holds great weight in the Shiite-led country, has also weighed in, threatening to encourage people to boycott the elections if there is a closed list.

Many Iraqis have rallied around the open list, saying it's more transparent.

If the lawmakers miss the deadline, Iraq will revert to voting guidelines used in the 2005 parliamentary elections, in which only party names were listed on the ballots.