A wave of attacks across Iraq on Sunday killed 54 people, while assailants bombarded Baghdad's heavily fortified Green Zone with mortar fire, sending US embassy staff scurrying into bunkers.

The deadliest attack was in the main northern city of Mosul where a suicide bomber crashed an explosives-laden truck into an Iraqi army base, triggering a blast that killed at least 12 soldiers and wounded dozens.

"The bomber smashed the truck through barriers at the entrance to the base and triggered the explosion" at around 7:00 am (0400 GMT), army officer Major Mohammed Ahmed told AFP.

The US military in a statement blamed the attack on Al-Qaeda and put the toll at 12 soldiers killed and 35 wounded.

Iraqi and US troops are engaged in a major offensive against Al-Qaeda in Mosul.

In a brutal attack in the south of Baghdad, armed men traveling in three cars opened fire on crowds in a local market in the mixed Zafaraniyah neighborhood, killing seven people and wounding 16, security and medical officials said.

In another attack in the Iraqi capital, a Katyusha rocket struck a residential building in largely Shiite eastern Al-Kamaliyah neighborhood, killing at least five people and wounding eight, security officials said.

A car bomb near a bus stop in Baghdad's Shiite Al-Shuala neighborhood killed five people and wounded eight others, security officials said.

Further north, a roadside bomb near the town of Al-Tuz, 75 kilometers (50 miles) south of Kirkuk, killed four Iraqi army personnel, a medic said.

The US military, meanwhile, said its troops raided a "suicide bombing network" in Diyala province northeast of the capital, killing 12 men, six of whom had shaved their bodies in ritual preparation for becoming human bombs.

Spokesman Major Winfield Danielson told AFP that the raid was launched east of the Diyala capital Baquba.

Elsewhere in Iraq, nine people were killed, including three from a Christian family in Baghdad when a mortar struck their home, police and medics said.

The violence on Sunday began with the first of four separate mortar attacks against the Green Zone, the seat of the Iraqi government and the US embassy.

The heavily-fortified area was struck another three times during the day in bombardments that injured at least four people and damaged buildings, officials and witnesses said.

Each attack sent staff of the US embassy scurrying for the shelter of nearby bunkers, witnesses said.

After the early morning onslaught, US attack helicopters were seen circling above the sprawling complex, which once served as Saddam Hussein's presidential compound.

"At least four people were injured" in one of the attacks, at 4.30 pm, a US embassy official told AFP. "The extent of the injuries is still being determined."

The official said another attack occurred around 8.30 pm but it was not immediately known whether damage or injuries were caused.

"We were warned to take cover," he said. "We are still trying to determine the extent and the impact of the attack."

An employee in the Green Zone, Mohammed al-Dulaimi, who witnessed the second attack, said eight mortar rounds fell near the US embassy complex and two a little distance away in a residential area.

"They caused slight damage and one sparked a fire," Dulaimi told AFP.

An embassy employee, who would not be named, said staff dashed for the embassy's bunker after the attacks.

"The first attack woke us up and people went rushing to the bunker. It was very frightening. The blasts were very close. Some people were in the showers and arrived with towels around them," she told AFP.

"Others were nonchalant and carried on as if nothing had happened. This was the worst attack since last summer, when some buildings in the embassy compound were hit by mortars."

PHOTO CAPTION 

US and Iraqi soldiers secure the site of a car bomb in Baghdad's Al-Shuala neighborhood.

AFP