At least 91 people have been killed and hundreds injured in a series of car bombs that rocked Baghdad and other Iraqi cities amid Eid al-Fitr celebrations, an interior ministry official said.

The attacks were the latest in spiralling violence which authorities have failed to stem, with the worst bloodshed in five years raising worries of a return to the all-out Sunni-Shia sectarian conflict that killed tens of thousands in past years.

The latest violence comes just weeks after brazen assaults, claimed by an al-Qaeda front group, on prisons near Baghdad that freed hundreds of fighters and which analysts warn could boost armed groups.

Overall, 17 car bombs and a series of shootings and other blasts killed at least 91 people and wounded over 300 across the country Saturday, security and medical officials said, as Iraqis celebrated the Eid al-Fitr holidays which follow the Muslim fasting month of Ramadan.

Al Jazeera's Imran Khan, reporting from the Iraqi capital, said 50 people had been killed in nine blasts in seven areas of the city on Saturday evening, in apparently coordinated strikes.

Car bombings

The blasts hit public markets, cafes, and restaurants, while violence earlier on Saturday killed two others in the capital, according to security and medical officials.

At Baghdad's Al-Kindi hospital, medics treated a man, apparently a soldier, whose face, chest and arms were covered in blood.

Medics sprinted into the hospital pushing people on stretchers, one of them a blanket-swathed man whose eyes were closed. Another man ran behind the stretcher, weeping as it was wheeled into the hospital.

Outside, long lines of cars inched along Baghdad roads, held up by increased security measures that came too late for the dozens of victims.

Also on Saturday, a suicide bomber detonated an explosives-rigged vehicle near a police checkpoint in Tuz Khurmatu, north of the capital, killing nine people.

A car bomb in Kirkuk, also north of Baghdad, killed an engineer.

Two car bombs in the southern city of Nasiriyah killed four, while a car bomb in the shrine city of Karbala left five others dead.

Elsewhere, three people were killed and five others wounded in separate attacks in Babil and Nineveh provinces.

More than 800 people died in attacks during the dawn-to-dusk fasting month of Ramadan, which began in the second week of July and ended this week.

Fighters struck targets ranging from cafes where Iraqis gathered after breaking their daily fast, to mosques where extended evening prayers were held during the month.

'Open war'

The violence came just weeks after attacks on prisons near the capital in which hundreds of inmates were freed.

Analysts, as well as global police organisation Interpol, have warned that the jailbreaks could lead to a rise in attacks, as the escapees were said to include senior al-Qaeda fighters.

The Interior Ministry has said the country faces an "open war" fuelled by Iraq's sectarian divisions and has attempted to boost security in Baghdad, closing roads and sending out frequent helicopter patrols.

Our correspondent said the withdrawal of American combat troops from Iraq 18 months ago has hit security efforts and emboldened Sunni fighters to step up attacks.

"People in the Iraqi security services will tell you ... that the Iraqi army is now on its own. They do not have the intelligence from the Americans that they had before. That has caused Sunni groups to go on the offensive.

"Then you have Shia groups taking revenge against them, in a classic tit-for-tat situation."

The United States condemned the perpetrators of the attacks as "enemies of Islam," in an unusually detailed statement. The State Department said that the car bombs and shootings were "cowardly" attacks "aimed at families celebrating the Eid al-Fitr" holiday.