US ambassador to Iraq unhurt by convoy bomb

(Recasts with U.S. embassy confirmation)

BAGHDAD, July 13 (Reuters) - A roadside bomb exploded near a convoy carrying U.S. ambassador to Baghdad Chris Hill in southern Iraq, but the envoy was unhurt, the U.S. embassy said on Monday.

Hill was travelling in Dhi Qar province, about 300 km (185 miles) southeast of Baghdad, on Sunday when the bomb struck his convoy, U.S. embassy spokeswoman Susan Ziadeh said.

"No personnel were injured or hurt. An investigation into the incident is taking place," she said.

The American daily USA Today said its reporter was a few minutes behind Hill in a separate convoy at the time.

"There was a bang and we went through a thick cloud of smoke," Hill told the reporter afterwards. "We are all fine."

Despite a sharp drop in violence across Iraq in the past 18 months, militants are still able to carry out frequent bomb attacks. U.S. forces withdrew from Iraqi cities at the end of last month, raising doubts about whether Iraq's own fledgling forces are up to the job of keeping the country safe.

Iraq is littered with munitions dumps from the time of Saddam Hussein, many of them left unguarded by U.S. forces after the 2003 invasion to oust him. Militants have since then had a steady supply of explosives with which to fashion home made bombs that can easily be concealed in pot holes or trash piles.

Largely Shi'ite southern Iraq has been mostly quiet since Iraqi forces launched a crackdown on militants loyal to anti-American Shi'ite cleric Moqtada al-Sadr last year. The U.S. military usually blames the sporadic attacks that do happen there on militias with links to Iran, a charge Tehran denies. (Reporting by Tim Cocks; Editing by Richard Balmforth)