<p>TIKRIT, Iraq (AP) — An Army Black Hawk UH-60 helicopter crashed Friday into a riverbank near Saddam Hussein's hometown of Tikrit, killing six U.S. soldiers, the military said. It probably was hit by a rocket-propelled grenade, an officer said. Two Americans also were killed in separate attacks Thursday and Friday in the northern city of Mosul, raising concerns that the insurgency was spreading north. "Six soldiers were on board and all of them were killed," said Maj. Josslyn Aberle, a spokeswoman for the 4th Infantry Division based in Tikrit. They were all from the 101st Airborne Division, she said.</p>