He said there could be more arrests. Some of those under arrest belonged to the now-illegal party under Mr. Hussein’s government. Mr. Maliki’s office declined to comment. But one of his advisers, insisting that he not be named because he was not authorized to speak, said the detainees were involved in “a conspiracy.”

The Ministry of the Interior is dedicated to Iraq’s internal security, and includes the police forces. The ministry has a history of being heavily infiltrated with Shiite militias, though it has improved considerably over the past two years.

A police officer, who knows several of the detainees but spoke on condition of anonymity for fear of retribution, said they were innocent, longstanding civil servants and had little in common with one another. Those who once belonged to the Baath Party were lower-level members, he said, insisting that the arrests were politically motivated.

Interior Minister Jawad Kadem al-Bolani, who has not been implicated and is out of the country, has his own political ambitions and has been expanding his secular Iraqi Constitutional Party. Iraq is a nation where leadership has often changed by coup, and as next month’s provincial elections approach, worry about violence is increasing. So are accusations about politically charged detentions.

The counterterrorism unit involved in these arrests is alleged to have conducted a raid this summer on the Diyala provincial governor’s office, during which an employee was killed and a provincial council member, one of the few Sunnis Arabs on the council, was arrested.

At a later protest against the arrest, several other Sunni politicians were detained. A number of politicians who follow the Shiite cleric Moktada al-Sadr, and who have set themselves up as political rivals to the prime minister, have also been arrested over the past months and charged with terrorist activities.

Anxieties about the government’s treatment of political enemies were also raised this week as the American military, as part of the recently approved security agreement, turned over to Iraqi custody on Monday 39 senior officials from the Hussein government. Some have been convicted already and others are scheduled to stand trial, the United States military said in a statement.