Iraqi resistance fighters killed two American soldiers north of Baghdad, and U.S. forces said Wednesday they were holding two key members of Saddam Hussein's Republican Guard. An attack 15 miles south of Tikrit, killed one U.S. soldier and wounded a second Wednesday when their four-vehicle convoy hit a roadside bomb, according to US military sources. The military also reported a soldier killed and two wounded in a bomb attack Tuesday near Taji, 12 miles north of the capital. The attack was in the same region where an oil pipeline fire sent flames 200 feet into the air. Also, an Iraqi boy was killed and at least four people wounded, a religious leader and witnesses said, in the first clash between US forces and Shiite Muslims in Baghdad since the war to oust Saddam Hussein. The result of this fight was four seriously wounded, and one young boy killed," Sheikh Ali al-Mutairi told AFP in Sadr City, the overwhelmingly Shiite neighborhood in Baghdad where the clashes occurred. Mutairi, who is deputy director of the Office of the Second Martyr attached to firebrand anti-occupation Shiite cleric Moqtada Sadr, and other witnesses said the violence flared in the morning after US efforts to remove a black Sadr flag from a communications tower. A US military helicopter hovered over the tower to remove the flag, but a female crewmember was beaten back by stick-wielding Iraqi men who had climbed the structure to defend their symbol, Mutairi and several others said. US forces responded by shooting in the air and ordering in six Humvees of troops to maintain order. Iraqi gunmen quickly responded with a round of gunfire at US ground troops, and a firefight broke out. "The shooting lasted about 20 minutes," Mutairi said. "They pulled out their troops," he said of the Americans, "and our heroes controlled the situation." As crowds swelled toward the area, Iraqi police arrived on the scene in an attempt to quell the unrest but were chased away amid death threats. A sheikh addressed the crowd with a loudspeaker, ordering them not to use violence until such an order was given by the Hawza, the respected Shiite religious authority in Iraq. Jalil Mahsen, 39, a labourer, told AFP he helped take several wounded Iraqis to hospital. "One boy was killed, and there are now 13 wounded in Al-Shouader Hospital," Mahsen said. Several thousand people were seen demonstrating at the site Wednesday afternoon and chanting anti-American slogans, as five flags including a new black Shiite banner were seen fluttering from the tower. "We are ready to commit suicide attacks against the Americans if we are told to do so," railed one of the demonstrators, dressed in the white shroud. The controversial Sadr has spoken out vehemently against the occupation and threatened to mobilize a so-called "Mehdi Army" of volunteer followers to rise up if called upon. **PHOTO CAPTION*** A US soldier observes the area as he guards a position north of Baghdad. Two US soldiers were killed and three wounded in two separate attacks on convoys.(AFP/Maxim Marmur)