(Adds police captain quote in paragraph 4)

KUT, Iraq, March 25 (Reuters) - Armed followers of Shi'ite cleric Moqtada al-Sadr seized control of five districts in the southern Iraqi town of Kut on Tuesday, police sources said.

The sources said Sadr's Mehdi Army militia were in control of the Jihad, Shuhada, Zahara, Sharqiya and Hawi districts of the city, which has 18 districts in total.

A Reuters witness in the city said he could hear shooting and explosions. U.S. warplanes were circling overhead.

"We ask U.S. forces to help us with aircraft and vehicles. The militants have spread out through Kut," said police Captain Majid al-Imara. He said 8-10 policemen had been wounded in clashes in the town of Aziziya north of Kut.

Iraq's security forces have repeatedly clashed with Sadr's followers in Kut over the past two weeks.

In Samawa, capital of southern Muthanna province, police imposed a curfew after Mehdi Army fighters appeared on the streets. Curfews were also imposed in Hilla and Kut, police said.

Sadr imposed a ceasefire on the Mehdi Army last August, a move the U.S. military said contributed greatly to falling levels of violence in Iraq.

But in recent days there have been signs that the truce is fraying, with Mehdi Army fighters complaining that Iraqi and U.S. security forces are exploiting it to target them.

Sadr called for nationwide sit-ins on Tuesday in protest against what he said were attacks on his followers and threatened a "civil revolt" if the crackdown did not stop. (Reporting by Jafar al-Tai in Kut; writing by Peter Graff in Baghdad)

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