BAGHDAD, Iraq — Al-Jazeera showed video Wednesday of an Indiana contractor who was kidnapped in Baghdad earlier this week and reported that he pleaded for Washington to save his life by withdrawing U.S. troops from Iraq.

Insurgents, meanwhile, set off a series of explosions, hitting a Defense Department convoy in an attack that killed five Iraqis and injured four U.S. contract workers, the U.S. military said. Another explosion near Kirkuk killed 12 police officers.

The U.S. Embassy said the man on the video appeared to be Jeffrey Ake, a contract worker who was kidnapped Monday while working on a water treatment plant near Baghdad.

A yellow ribbon was tied around a tree outside Ake's one-story brick house in LaPorte, Ind. An American flag fluttered on a pole from the house.

Ake, 47, is president and CEO of Equipment Express, whose products include machines that fill water bottles.

LaPorte Police Chief David Gariepy met with Ake's family and called it "a terrible situation."

"We have to keep them in our thoughts and pray for his safe return," Gariepy said. "It devastates all of us as Americans when someone from our country is involved in something like this."

Ake spoke on the video, but only a few words could be heard in the broadcast. Al-Jazeera reported that he asked the U.S. government to begin withdrawing from Iraq and to save his life. No group claimed responsibility for the abduction.

White House press secretary Scott McClellan said the administration is keeping in touch with the family of the captive contract worker, but he said there would be no negotiating with the kidnappers.

"Anytime there is a hostage — an American hostage, it is a high priority for the United States," he said "Our position is well known when it comes to negotiating. Obviously this is a sensitive matter."

More than 200 foreigners have been taken captive in Iraq in the past year, and more than 30 have been killed.

Al-Qaida in Iraq said in an Internet statement that it carried out the deadly car bomb in Baghdad, which the military said damaged two SUVs and five cars. The explosion left charred and burning cars on the dangerous road to Baghdad's airport.

"A member of our martyrdom seekers' brigade mingled in an American military convoy at the airport road and exploded himself, destroying the infidels," al-Qaida in Iraq said in an Internet statement. The statement could not be independently verified.

The car bomb was among four explosions that rocked central Baghdad early Wednesday, the military said. The second was a car bomb that didn't cause any damage, and the third was a "secondary explosion" nearby, the military said.