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.
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"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.