In a response to widespread criticism and President Bush’s new Baghdad security plan, the Iraqi government has arrested more than 400 members — including several dozen “senior” leaders — of Iraq’s most powerful Shiite militia, officials said Thursday.

According to reports from various news outlets, Iraqi Prime Minister Nouri al-Maliki made the claim in an interview Wednesday with foreign journalists.

Maliki reportedly said that the crackdown against the Mahdi Army had taken place “within the last few days” and that the number arrested was near 420. And, Iraqi officials said, those arrested are not being immediately released. In previous operations against militias, U.S. military officials have complained that political and sectarian ties have led to temporary arrests amounting to nothing.

The militia is led by the radical cleric Muqtada al-Sadr, who ordered his men into open battle with American troops in 2004. Since then, however, the militias have largely shied from direct confrontations, instead allegedly leading Shiite reprisals and sectarian killings. Al-Sadr then turned to the political arena, throwing his support behind Shiite politicians.

U.S. military officials have previously said they believe there are around 7,000 Mahdi Army members in Baghdad.