At least 38 people were killed and 74 others wounded Saturday when a suicide bomber stepped onto a bus carrying Shiite pilgrims in Iraq and detonated himself, police officials said.
The attack -- which occurred between Baghdad and Samarra -- was the second targeting pilgrims in the last three days.
The suicide bomber detonated at least 10 kilograms of explosives concealed in his vest, Samarra police officials said.
Most of the casualties were Shiite pilgrims heading back south to Nasiriya from Samarra in the north. Some of the wounded were on other buses waiting at the security checkpoint where the attack occurred.
The pilgrims had journeyed to commemorate the death of Imam al-Askri, who died in 874 A.D and is buried at a Samarra mosque.
On Thursday, a suicide bomber drove into a rest tent for Shiite pilgrims north of Baghdad, killing eight people and injuring 30 others, police said.