"We have found four bodies, including of a woman" at the site near Karbala, central Iraq, civil defence official Abdelrahman Jawdat told AFP.

Between six and eight pilgrims had been reported trapped under the debris of the shrine, known as Qattarat al-Imam Ali, civil defence spokesman Nawas Sabah Shaker had said earlier.

Three children have been rescued following Saturday's disaster, emergency services said, adding that they were in "good condition" and being monitored in a hospital.

Rescue teams working through the night were able to provide supplies of oxygen, as well as food and water to some of those trapped through gaps in the rubble, state news agency INA said.

Iraqi President Barham Saleh on Twitter called on the "heroic" rescue workers to "mobilise all efforts to save the trapped people".

The emergency responders said earlier they were maintaining verbal contact with the victims "to reassure them".

"We are working hard, with the utmost precision, to reach" those trapped, said Jawdat, director of the civil defence media department.

"Any mistake could lead to further collapses."

One man at the scene, Bassem Khazali, said his nephew was among those buried.

"I am afraid that all the efforts undertaken will be in vain... We want to know what happened, why it happened," Khazali told AFP.

- Sand, rocks collapse -

Shaker told AFP that "sand dunes and rocks collapsed onto the shrine building", blaming the saturation of the earth that had been caused by humidity.

The landslide on Saturday afternoon hit the shrine located in a natural depression about 25 kilometres (15 miles) west of the Shiite holy city of Karbala.

The rocks and sand started sliding because of the "saturation of the earthen embankment adjacent to the shrine", the civil defence told INA.

"This led to the collapse of about 30 percent of the area of the building, which measures about 100 square metres (1,000 square feet)."

Iraq's holy city of Karbala is the burial place of Imam Hussein, grandson of the Prophet Mohammed.

Shiites view Hussein, who died in battle in AD 680, as the rightful successor to the Prophet Mohammed, the issue at the heart of a schism with Sunni Islam.

The stricken shrine is dedicated to Imam Ali, the son-in-law of the Prophet Mohammed, who according to Shiite tradition stopped there with his army on his way to a battle in AD 657.