Twenty people, including 13 Iranian pilgrims, were wounded in bomb attacks in Iraq on Sunday, an interior ministry official said, while insurgents launched rocket and bomb attacks on US forces.

A roadside bomb targeting a bus carrying pilgrims wounded 15 people, among them 13 Iranians, in the Kadhmiyah area of north Baghdad, the official said.

And two other roadside bombs wounded five more people in Taji, 25 kilometres (15 miles) north of the capital, the official added.

The US military said four Katyusha rockets targeted its Forward Operating Base Warrior in the disputed oil-rich province of Kirkuk in northern Iraq. "There were no damage or casualties," a military spokeswoman said by email.

And on Saturday evening, a roadside bomb targeted a US convoy in the Taji area, without causing casualties or damage, the military said.

All of the roughly 27,000 US soldiers remaining in Iraq are to depart by year's end. Ten American bases have yet to be handed over.

Violence has declined nationwide since its peak in 2006 and 2007, but attacks remain common. A total of 258 people were killed in October, according to official figures.