Four U.S. Marines were wounded in central Baghdad Thursday when a man strapped with explosives approached a checkpoint and blew himself up.

There were unconfirmed reports that one or more servicemen had been killed.

The suicide attack occurred about 7:30 p.m. (11:30 a.m. EDT) near Saddam City, a sprawling, poor neighborhood that is home to a large Shiite population.

Marine Capt. Joe Plenzler, public affairs officer with the 1st Marine Division, said the attacker approached a Marine checkpoint and detonated himself. The suicide bomber was killed.

"It confirms what we expected," Plenzler said. "We expected the enemy would try to pull all the dirty tricks out of the bag," he said.

No information was immediately available on whether there were civilian casualties.

The Iraqi regime had warned that suicide attacks would be "routine military policy," and American troops have been wary of approaching civilians.

A week ago, two Iraqi women blew themselves up in an attack on U.S. forces, killing three American soldiers in western Iraq.

On March 29, a bomber posing as a taxi driver pulled up to a roadblock north of Najaf, waved to American troops for help, then blew up his vehicle up as they approached, killing four..

On Sunday, U.S. soldiers killed six Iraqi fighters wearing the head bands and clothes of Islamic suicide attackers on the southern outskirts of Baghdad.

The Associated Press contributed to this report.