BAGHDAD, Iraq, April 17 — American and Iraqi troops sealed off one of Baghdad's most prominent Sunni Arab neighborhoods on Monday after a night of raging gun battles that left homes and storefronts riddled with bullets and at least one civilian dead, Iraqi officials and witnesses said.

The closure of Adhamiya, in northern Baghdad, seemed to signal deteriorating security in a neighborhood where attacks on American and Iraqi forces had ebbed in recent months. The area is home to hard-line Sunni Arabs who remain hostile to the Shiite-led government and American presence. At its center is the well-known Abu Hanifa Mosque, where Saddam Hussein made his final public appearance in April 2003 before fleeing Baghdad and the American invasion force.

A leading Sunni Arab political group, the Iraqi Islamic Party, released a statement on Monday calling for calm and saying that a "human disaster might occur." It said the clashes were between Iraqi government forces and residents of Adhamiya, implying that the uniformed forces were the aggressors.

At least one civilian was killed and five injured in the battles, an Interior Ministry official said.