KUT, Iraq — Bomb blasts ripped through more than a dozen Iraqi cities this morning, killing 56 people — most of them in the southern city of Kut — in a wave of violence that shattered what had been a relatively peaceful holy month of Ramadan.

The violence struck from the northern city of Kirkuk to the capital of Baghdad to the southern Shiite cities of Najaf, Kut and Karbala, and emphasized the persistent ability of insurgents to wreak havoc at a time when Iraqi officials are weighing whether they are able to protect the country without the assistance of American troops.

The blasts were coordinated to go off in the morning and included a combination of parked car bombs, roadside bombs and a suicide bomber driving a vehicle that rammed into a police station.

The scope of the violence — seven explosions went off in different towns in Diyala province alone — emphasized the dangerous ability of insurgents to carry out attacks despite repeated crackdowns by Iraqi and U.S. forces.

The worst violence came in the southern city of Kut, 100 miles southeast of Baghdad, where twin explosions went off as workers were gathered in a market selling generators and other appliances. Police spokesman Lt. Col. Dhurgam Mohammed Hassan said the first bomb went off in a freezer used to keep drinks cold. Then as rescuers and onlookers gathered, a parked car bomb exploded.

Violence has dropped in Iraq from the heyday of the war when such bloody bombings were an almost daily occurrence. But the persistence of the violence in Iraq underscores the ability of insurgents to undermine the country’s security.

The blasts were the first major act of violence since Iraq’s political leaders earlier this month announced that they would begin negotiations with the United States over whether to keep a small number of American forces in the country past Dec. 31.

All American forces are to leave the country by the end of this year, but both Iraqi and U.S. officials have expressed concern about the ability of Iraqi forces to protect the country.