BAGHDAD, May 13 (Reuters) - Gunmen launched numerous attacks on U.S. troops in the Baghdad bastion of Iraqi Shi'ite cleric Moqtada al-Sadr overnight, the U.S. military said on Tuesday, in a sign that many militia are ignoring a pact to halt fighting.

Iraqi police said 11 people had been killed and 20 wounded in fighting during the night in the Sadr City slum in eastern Baghdad. They gave no details on the casualties.

A spokesman for U.S. forces in Baghdad, Lieutenant-Colonel Steven Stover, said troops killed at least three gunmen in separate incidents after being attacked multiple times.

Iraq's ruling Shi'ite alliance and Sadr's opposition movement in parliament reached an agreement on Saturday to end seven weeks of fighting in Sadr City that has killed hundreds of people. The two sides formally signed the agreement on Monday.

But it has long been unclear how much control the anti-American Sadr has over some of the tens of thousands of gunmen who profess allegiance to him.

The fighting was triggered when Prime Minister Nuri al-Maliki ordered an operation against Shi'ite militias in the southern city of Basra in late March.

The offensive sparked fierce resistance from Sadr's Mehdi Army militia. While fighting with security forces eased in Basra within a week, clashes with gunmen quickly spread to Sadr City. (Reporting by Tim Cocks; Writing by Dean Yates; Editing by Giles Elgood)

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