Baghdad, Iraq ? Insurgents battled American troops in the streets of Baghdad on Saturday, killing a U.S. soldier in an ambush and gunning down four government employees in signals that the guerrillas remain a potent force despite the fall of their stronghold of Fallujah. Nine Iraqis also died in fighting west of the capital.

In Fallujah, where U.S. Marines and soldiers are still battling pockets of resistance, insurgents waved a white flag of surrender before opening fire on U.S. troops and causing casualties, Marine spokesman 1st Lt. Lyle Gilbert said Saturday without elaborating.

Al-Arabiya television quoted Iraqi guerrillas fleeing Fallujah as saying they had run out of ammunition and many fighters who stayed behind were badly wounded.

U.S. troops in the northern city of Mosul found the bodies of nine Iraqi soldiers Saturday, all shot in the back of the head. The military first reported that seven of the victims were beheaded, but a second statement issued later Saturday said those reports were false.

Four decapitated bodies found earlier in the week in Mosul have not been identified, the military said Saturday. American and Iraqi forces detained 30 suspected guerrillas overnight in Mosul, the U.S. military said.

In a positive development, a Polish woman abducted last month in Baghdad reappeared Saturday in Poland after being suddenly released. Teresa Borcz Khalifa, 54, refused to say how she was freed but said her captors treated her “properly” — treatment that they told her was “motivated by their religious beliefs.”

But the widespread clashes in Baghdad — which broke out early Saturday in at least a half-dozen areas — and other areas of central and northern Iraq underscored the perilous state of security in this country after 18 months of American military occupation — and just more than two months before vital national elections.

People look at a truck on fire after a suicide car bomb exploded Saturday in central Baghdad, killing at least one person.