A US soldier and an Iraqi guardsman have been reported killed and others injured in a car bomb that rocked the Green Zone in Baghdad, journalists and hospital sources said. Ziyad al-Samarrai, an Iraqi journalist, told Aljazeera from Baghdad: "A US soldier and an Iraqi National Guard were killed in the explosion on Tuesday." A US military spokesman, however, said no US personnel were hurt. The blast comes a day after a similar strike at the Green Zone's western gate. Hospital officials have confirmed that at least 13 people have been injured, al-Samarrai said. "All roads leading to the site have been closed off by US forces, preventing reporters from approaching it," said al-Samarrai. "US forces, Iraqi police and the national guards cannot control such attacks any longer, particularly the suicide operations targeting them. They cannot even face these attacks. They only set up checkpoints." **Battlefield*** "Such attacks take place almost daily. Iraqi resistance fighters are able to turn the country into a battlefield whenever they want to," he added. Iraqis working with US forces areroutinely attacked in Baghdad The blast, which sent a large plume of smoke over the city, occurred at a different entrance to the zone than that targeted on Monday, where a car bomb killed seven Iraqis and injured 19. A national guard officer said there were many wounded in Tuesday's blast, which occurred at 8.20am (0520 GMT). At least 13 of the wounded, most of them in a serious condition, were taken to Baghdad's Yarmuk hospital, according to Dr Raad Abd al-Jabbar. **Car bomb*** "There's been a VBIED [vehicle-based improvised explosive device] at Checkpoint 12," the spokesman said. A wounded Iraqi said he saw at least two people dead "I saw a Kia car drive through the checkpoint and it exploded," said bus driver Muhammad Kadhim as he lay wounded at the civilian Yarmuk hospital. "I'm sure two National Guards next to it were killed," he added, although the US spokesman said he knew of no Iraqi military casualties. "Two of the people standing next to me were killed. I saw them cut to pieces," said another wounded man, Firas Sahir, a labourer who was lining up to go into work in the Green Zone. Isan Nasir, an official who keeps patient records at Yarmuk hospital, said 12 people, all men, had been brought in wounded and there were no dead bodies at the hospital, though that might change. **Frequent target*** Monday's explosion occurred when an attacker detonated his car as he was waiting for his vehicle to be searched at a checkpoint, Iraqi national guards said. Two mortar rounds landed in the Green Zone, which houses the interim Iraqi government and embassies, later the same day. And on 4 December a car bomb exploded at a police station outside one of the zone's main entrances. **PHOTO CAPTION*** A US soldier watches two security men inspect the site where a car bomb exploded in Baghdad Tuesday Dec. 14 2004. (AP)