Iraqi police arrested 19 officials and tribal leaders after they threatened to harm an MP who alleged graft in Baghdad's municipal government, officials said on Saturday.

Sherwan al-Waili, a lawmaker belonging to Prime Minister Nuri al-Maliki's bloc and a former minister of state for national security, made the claims in mid-December. They led to the arrest of Baghdad deputy mayor Naeem Abboub.

The 19 suspects, including at least five Baghdad municipal officials and several tribal leaders, were detained on Friday after they allegedly conveyed the threat to Waili's brother Merdan in the southern city of Nasiriyah.

"Around 20 men arrived, some of them in government cars," Merdan al-Waili, a 60-year-old tribal chief, told AFP.

"They threatened me. They said: 'If our sons are not released in two days, you will see what happens'."

Nasiriyah police Colonel Falah al-Saidi said officers arrested 19 people after they "threatened Merdan, and said his brother is responsible for the lives of their sons, and the judgments against them."

Thirteen of the people arrested have since been released, and six remain in custody.

A Waili family member, who did not want to be named, said the group had also demanded that the lawmaker publicly apologise for his claims.

Waili's political office told AFP that the lawmaker had uncovered evidence of corruption in Abboub's office, and insisted Waili would continue his work.

Graft is rife in Iraq, with watchdog Transparency International ranking the country as the eighth-most corrupt country in the world. Efforts to fight corruption are often met with violence and intimidation.

Police kill senior Al-Qaeda in Iraq leader
Baghdad (AFP) Jan 21, 2012 - Police killed a senior leader of Al-Qaeda's front group in Iraq in clashes while attempting to arrest him on Saturday, the interior ministry said in a statement.

Majid Hassan Ali, head of the Islamic State of Iraq's operations in the main northern city of Mosul, was killed and 19 Al-Qaeda fighters, two of them Palestinian, arrested in the gunfight south of the city.

"The third division of the federal police ... killed the chief of the ISI in Mosul," the statement said.

It said Ali, who is also known as Abu Ayman, was hiding in the village of Rufaila, just outside Mosul, a former Al-Qaeda bastion in which the jihadists retain a foothold, when federal police forces conducted an assault on the area.

"During the arrests, heavy clashes erupted between the police and the terrorists," the statement said. "During these clashes, he was killed and 19 terrorists were arrested, including two Palestinians."

Federal police officers recovered magnetic "sticky bombs", roadside bombs, and several bags of explosives, as well as weapons and ammunition as a result of the operation, according to the statement.

The ISI, while regarded by analysts and officials as much weaker now than at the height of the sectarian bloodshed that rocked Iraq from 2006 to 2007, remains capable of mounting spectacular mass-casualty attacks.

While violence is down across Iraq, attacks remain common, especially in Mosul. More than 200 people have been killed in violence since the December 18 withdrawal of US forces.