Iraqi security forces have arrested a top official of a Shi'ite militia stronghold, as part of a new military operation in the south of the country.

Security officials say police seized the mayor of the city of Amarah along with a local council member during the sweep Thursday in Maysan province. Officials say police have arrested at least 12 people since the new crackdown on militants began today.

U.S. commanders say the region is used as a base to smuggle weapons from neighboring Iran. In recent days, Iraqi security forces have urged fighters in the area to hand over their weapons.

Maysan province also is a stronghold of radical Shi'ite cleric Moqtada al-Sadr and his Mahdi Army militia. Sadr aides have said his followers will not resist Iraqi forces.

The operation is the latest effort by Iraqi Prime Minister Nouri al-Maliki to combat Shi'ite militias. It follows similar crackdowns in the southern city of Basra and in Baghdad's Sadr City.

In northern Iraq Thursday, coalition forces say they detained 21 suspected terrorists during operations targeting al-Qaida in Iraq.

Some information for this report was provided by AFP, AP and Reuters.