Iraq's national security advisor says four guards protecting the Shi'ite shrine bombed last week north of Baghdad are being held as suspects in the attack.
In an interview with Reuters news agency, Mowaffaq al-Rubaie said six others have also been arrested in connection with the blast at the Askariya shrine in Samarra.
State Security Minister Abdul Karim al-Enazy is quoted as saying the case grew out of questions over why the bombers, who spent hours planting explosives, did not kill any of the guards.
Hundreds of people have been killed in reprisal attacks since the February 22 bombing, including at least 60 people Tuesday. Police say 15 of the latest fatalities came in a bombing outside a Shi'ite mosque in Baghdad.
Meanwhile, prosecutors at the trial of Saddam Hussein have presented a 1984 document they say shows Saddam approved the execution of 148 Shi'ite Muslim villagers.
The document, said to have been signed by Saddam, was entered into evidence Tuesday, as the trial resumed after a two-week break.
Saddam and seven co-defendants face death by hanging if found guilty of executing the villagers in 1984, after a failed assassination attempt against Saddam. The trial is set to resume Wednesday. Some information for this report was provided by Reuters.