An Iraqi insurgent group said it killed a kidnapped U.S. security consultant Thursday, making the claim through an Internet posting.

The posting surfaced on an Islamic militant Web forum. The group, calling itself the Islamic Army, said it will release images of the killing at a later time. It did not identify the hostage, although in an earlier statement named him as Ronald Alan Schulz.

The White House has not confirmed the claim, nor has it confirmed the hostage's name.

"Any time there is an American that is taken hostage it is a priority for the administration, and their safe return is a priority for the administration," White House press secretary Scott McClellan told The Associated Press.

In the posting, the insurgents said the apparent killing was in retaliation for U.S. President George Bush's refusal to negotiate with the group.

"The war criminal Bush continues his arrogance, giving no value to people's lives unless they serve his criminal, aggressive ways," the posting reads. "Since his reply (to the demands) was irresponsible, he bears the consequences of his stance.

"Therefore the American security consultant for the Housing Ministry was killed after the end of the deadline set to respond to the Islamic Army's demands."

Bush has often said he will not pay ransom for hostages. On Tuesday, he told reporters he would instead use "intelligence-gathering to see if we can't help locate them."

An American, Tom Fox, is also being held hostage by the Swords of Righteousness, the same group that is holding Canadians James Loney and Harmeet Sooden, along with Briton Norman Kember.

All four hostages are part of the humanitarian group Christian Peacemaker Teams.

The Swords of Righteousness has set a Saturday deadline, threatening to kill the four humanitarian workers if its demands are not met. It was originally set for Thursday.

In total, seven Westerners have been abducted in Iraq since Nov. 25.

Bus attack

Earlier Thursday, a suicide bomber detonated a belt of explosives in a bus, killing 32 people and wounding 44 others.

Most of the dead were in the bus. Police said that the death toll also included some who were gathered at a food stall nearby.

The bus had been on its way to the Shiite city of Nasiriyah, 320 kilometres southeast of Baghdad, according to police Lt. Ali Mitaab.

The attacker apparently jumped on the bus just as it was pulling away from the station, to avoid security checks, police said.

"As the bus was going outside the station, a man carrying a bag tried to get into the bus, but the conductor was suspicious about him," police Lt. Wisam Hakim said. "He tried to stop him but the man insisted. He sat in the middle of the bus and then the explosion took place."

The station where Thursday's bombing took place has seen violence before. Last August, a triple car bombing there killed at least 43 people and injured close to 90 more.