Fighting has erupted across Baghdad, starting with several pre-dawn blasts in the Green Zone, the protected area where offices belonging to the Iraqi interim government, coalition forces and foreign embassies are located. At least 35 Iraqis are reported dead in a day-long series of attacks.
Strong explosions believed to be caused by mortars or rockets shook central Baghdad before dawn. Plumes of black smoke could be seen billowing into the sky from the Green Zone.
The heavily protected Green Zone is the site of frequent attacks. But this barrage was one of the most intense in several weeks.
U.S. forces also fought a gun-battle with insurgents on Haifa street, a central Baghdad boulevard. Four U.S. soldiers were injured when their Bradley fighting vehicle was set on fire. A U.S. helicopter attacked targets in the area, which witnesses say killed several people.
U.S. troops also battled insurgents in Ramadi, a militant stronghold west of Baghdad.
Saturday, Iraqi Minister of State Kasim Dawood announced a fresh nationwide offensive against loyalists to the Saddam Hussein government, militants and terror groups.
"Always, terrorists try to target different areas in Iraq to show that the instability is the main character of the country," Mr. Dawood said. "We will deal with these activities."
In recent weeks, U.S.-led forces have pushed further into insurgent strongholds, including the Baghdad slum area of Sadr City and Fallujah, where a siege against militants failed earlier this year. U.S. fighter planes conducted four days of airstrikes against Fallujah in the past week.
In the north, coalition troops have also targeted the northern town of Tal Afar, which the U.S. military says is a key crossing point for foreign fighters entering Iraq from Syria.
A car-bomb was also detonated outside the gates of the Abu Ghraib prison west of Baghdad, wounding at least three people. On Saturday, a U.S. military intelligence soldier, Armin Cruz, was sentenced to eight months in jail for his part in the abuse of detainees at the prison.