Ramadi, Iraq ? A bomb blast turned a parade of U.S.-trained police cadets into a deadly zone Saturday, killing seven and injuring dozens in an attack U.S. officials blamed on insurgents targeting Iraqis who work with Americans.

As mosque loudspeakers in the western city of Ramadi wailed for blood donations for the wounded, angry Iraqis said the victims had been told that collaborating with the Americans would come to no good.

The top U.S. official in Iraq said “desperate men” were leading the anti-American attacks in a campaign blamed on loyalists of the ousted Saddam Hussein.

“Those who refuse to embrace the new Iraq are clearly panicking, they are turning their sights on Iraqis themselves,” L. Paul Bremer said. “Today they have killed innocent Iraqis with the same disdain toward their own people they showed for 35 years.”

A British television journalist also was shot and killed Saturday outside the Iraqi National Museum in Baghdad in another sign of unrest.

In northern Iraq, U.S. troops raided a Turkish special forces office and detained 11 soldiers, further straining U.S.-Turkey diplomatic ties. A Turkish newspaper reported the men were detained after rumors that they were plotting to kill a senior Iraqi official in Kirkuk, 175 miles north of Baghdad.

Turkish Prime Minister Recep Tayyip Erdogan called the detentions an “ugly incident” and demanded the soldiers’ release. The United States was responding, releasing some of the soldiers by Saturday evening, but not all, Erdogan said.

In Ramadi, the graduating police were marching from a boys school where they underwent five days of training to a nearby government building when a massive blast tore into them.

Even as they step up their ambushes on U.S. troops, Iraqi insurgents have begun targeting the security services and civilian infrastructure U.S. forces are trying to rebuild, such as police forces, oil pipelines and Baghdad’s electricity grid.

Also Saturday, the human rights group Amnesty International issued a report lambasting the United States and Britain for failing to bring Iraq’s postwar lawlessness under control. The report said “millions of Iraqi men, women and children are paying a terrible price” for the failure to control rampant crime, and it demanded urgent action.

The U.S.-led provisional government says it is working hard to restore order.