A roadside bomb in Iraq's Anbar province wounded 19 Pakistani Shiite pilgrims on Sunday, police and a doctor said, in the second attack against pilgrims in the Sunni province in days.

"A bus carrying Pakistani pilgrims was targeted by a roadside bomb at around 4:00 pm (1300 GMT) on the highway to Baghdad" from Fallujah, Anbar police spokesman Lieutenant Colonel Hassan Taher Kitab told AFP.

The attack wounded the driver of the bus and 18 passengers, including three children who were in critical condition, he said.

Assem al-Hadithi, a doctor at Fallujah Hospital, confirmed the toll, and said that the pilgrims were going to visit the Al-Askari Shiite shrine in Samarra, north of Baghdad.

The attack comes after a roadside bomb exploded on Wednesday near a bus carrying Lebanese Shiite pilgrims west of Anbar's provincial capital Ramadi, killing three and wounding at least 10.

Iraq is home to some of the holiest sites in Shiite Islam, to which hundreds of thousands of pilgrims flock each year. Pilgrims are periodically attacked, often with bombs.

Brutal sectarian fighting tore across Iraq beginning in 2006, leaving tens of thousands of people dead.

While the violence was brought under control by a US troop surge and by Sunni tribesmen switching sides to fight against insurgents, sectarian tensions in Iraq remain high.