U.S. troops have discovered four decapitated bodies and captured dozens of militants during operations to purge northern Mosul (search) of insurgents, the military said Saturday.

All four bodies, whose identities were not established, were found on Thursday, and have been turned over to Iraqi authorities, said Lt. Col. Paul Hastings, a spokesman for Task Force Olympia (search).

Three of the bodies were found by the roadside in a northeastern neighborhood of Mosul, while the fourth body was discovered in the southwestern part of the city, he said.

"Our troops came across them. They were by the roadside," Hastings said.

On Friday, a statement posted on an Islamist Web site in the name of Jordanian terror leader Abu Musab al-Zarqawi (search)'s group said it had "slaughtered" two Iraqi National Guard officers "in the presence of a big crowd" in Mosul. The claim included no photos or video and could not be verified.

There was no way of saying whether the bodies had been decapitated in a public manner, as the Web site claimed, said Hastings, adding that U.S. troops were "not able to identify them and say whether they were bodies of Iraqi National Guard, police or just anybody."

During raids Friday, Iraqi commandos and U.S. forces detained 30 suspected militants, including three suspected of belonging to a terrorist cell. The military said the men were being questioned.

U.S. and Iraqi troops began a major military operation Tuesday after insurgents launched an uprising in Mosul late last week, taking control of some parts of the western half of the city, and stormed police stations, bridges and political offices.

In fighting late Thursday, Iraqi military and police units killed 15 insurgents and captured 10, according to Deputy Gov. Khasro Gouran. Later, Iraqi forces backed by American troops raided a hospital allegedly used by insurgents, detaining three people, U.S. officials said.

A car bomb attack Friday on a U.S. patrol in Mosul injured one American soldier, the U.S. military said.

Mosul, Iraq's third largest city with more than a million residents, is 225 miles northwest of Baghdad.