American troops detained the U.S.-appointed mayor of this Shiite (search)-dominated southern city on Monday, accusing him of kidnapping and corruption, and arrested 62 of his top aides, the military said.

Abu Haydar Abdul Mun'im (search) was installed by the Americans shortly after they entered this city in April. But the former army colonel was unpopular among the local population because of his background in ousted Iraqi leader Saddam Hussein's military.

He was replaced by Haydar Mahdi Mattar al-Mayali, a former deputy in the mayor's office.

Coalition forces made the arrest at the request of an Iraqi investigative judge in Najaf (search), said a statement by the U.S.-led provisional authority.

"They have been investigating these allegations for some time before concluding that there is sufficient evidence to warrant arrest," the statement said. "These allegations are very serious."

On Monday, U.S. forces blocked the entrance to Mun'im's offices and would not let reporters enter. "There is a mission in progress," one Marine said.

In addition to kidnapping, Mun'im stands accused of holding hostages, pressuring government employees to commit financial crimes, and attacking a bank official.

In recent weeks, residents of Najaf (search), 110 miles southwest of Baghdad, have held demonstrations against Mun'im, accusing him of links to Saddam's dissolved Baath Party (search).

Saddam was highly unpopular in the Shiite-dominated south, which until recently had been largely free of the ambushes that have been plaguing U.S. troops in the so-called Sunni triangle (search) north and west of Baghdad, where Saddam enjoyed a degree of support.

U.S. and British troops, which have a large presence in the south, have been seeking to win favor among the local population.