CAIRO (Update 5) - Egypt's army rulers imposed a curfew on Cairo's Tahrir Square and downtown area, state media announced on Sunday, after 23 people were reported killed in clashes between Christians and military police in the center of the capital. Christians protesting against an attack on a church clashed with military police, witnesses and security sources said, in fighting that spread across the downtown area. The curfew would last from 2 am to 7 am (0000-0500 GMT) on Monday, state TV reported.