U.S. and allied forces clash with supporters of the radical Shiite cleric Muqtada al-Sadr. The worst violence was near the southern city of Najaf, where 20 Iraqis were killed when al-Sadr's supporters opened fire on a Spanish garrison near the city. There was a similar demonstration in the Sadr City neighborhood of Baghdad. The violence flared after U.S. forces detained an associate of Sadr. Hear NPR's Philip Reeves and NPR's Howard Berkes.