A bomber wearing an Iraqi military uniform struck a U.S. military delegation visiting the mayor of violence-wracked Baqouba on Monday, injuring at least eight American soldiers and nine others.

Police officials claimed the attacker was disguised as a soldier — a tactic used in the past to pass through checkpoints — but U.S. forces have faced attacks from actual members of the security forces as well.

In February, two police officers opened fire on U.S. soldiers in the northern city of Mosul, killing one and raising worries about insurgent infiltration in security forces.

The Baqouba attack occurred as a group of Iraqi officials, led by Mayor Abdullah al-Hiyali, waited at the main gate of the municipal building to greet the U.S. soldiers, said Raad al-Dahalaki, the deputy mayor.

"When the U.S. soldiers left their vehicles and started to walk toward the building, a man wearing a military uniform mingled with the crowd of U.S. soldiers and Iraqi policemen and set off the explosion," said al-Dahalaki.

The U.S. military said at least eight soldiers were wounded in the blast.

Iraqi security officials said at least nine civilians were also hurt. The officials spoke on condition of anonymity because they were not authorized to speak to media.

Baqouba, 35 miles (60 kilometers) northeast of Baghdad, is the capital of the Diyala province — which remains one of the centers for the Sunni insurgency despite an overall drop in violence around the country.

U.S. and Iraqi security forces have stepped up offensives in Baqouba and the northern city of Mosul in attempts to break the last insurgent strongholds.

In Baghdad, more than 60 mourners attended the funerals of three jewelry store owners killed Sunday in daylight robberies by gunmen carrying weapons with silencers. Prime Minister Nouri al-Maliki ordered a special task force to investigate the slayings.

Iraqi authorities are under pressure to show a decisive response to security threats as U.S. forces increasingly pull back from frontline roles. Although violence is sharply down compared with past years, a wave of high-profile attacks have brought worries that the relative calm may not last.