Baghdad ? A series of car bombs ripped through downtown Baghdad early today, killing four people and wounding as many as 15 near the heavily fortified Green Zone, Iraqi police officials said.

At least three explosions were set off within minutes of each other, shortly after 7:30 a.m. (10:30 p.m. CST Monday), the two police officials said.

U.S. military spokesman Army Lt. Brian Wierzbicki, said at least three or four explosions occurred outside the Green Zone, the heavily fortified area in the center of Baghdad that houses the U.S. Embassy as well as the Iraqi prime minister’s office. He did not have any immediate casualty reports.