BAGHDAD - A wave of early-morning explosions in and around the Iraqi capital killed 16 people and wounded dozens Sunday, and for the third time this month, Iraqi security forces were the main target.

Insurgents have been hammering the security forces in an attempt to undermine Iraqis' confidence in the ability of their police and military to take over from U.S. forces, which are scheduled to leave the country by the end of the year.

At least nine of those killed were police officers, underscoring the risks of the job.

"The aim of these attacks is to send a message to the locals: 'If the security people cannot protect themselves, then how can they protect you?' " said Iraqi police Capt. Majid Mohammed Amin, who joined the force in 2000 and who has since survived two roadside bombings.

The worst single attack Sunday was near the city of Taji, 12 miles northwest of Baghdad. It was an almost textbook insurgent ambush. First, a roadside bomb targeting a U.S. military convoy exploded. When police arrived, a suicide bomber walked into the crowd and blew himself up, police and hospital officials said.

Seven police and three civilians were killed, and 19 people, including 15 police officers, were injured, officials said. Earlier, at least 10 bombs exploded around the capital at the start of the workweek.

About 7 a.m., a car bomb in a parking lot in eastern Baghdad's Sadr City neighborhood exploded, injuring five people and damaging cars.

Minutes later, also in Sadr City, a bomb hidden in a pile of garbage exploded, killing one person and wounding five more. Five minutes later, a roadside bomb targeting a police patrol exploded; three policemen and four bystanders were injured in that blast.

In the southwestern neighborhood of Bayaa, five explosions went off in rapid succession, killing five people, including two policemen, and injuring 15 people, including six policemen, police and hospital officials said. Other bombs went off in the upscale Karradah neighborhood.