The toll from a suicide bombing that targeted Shi'ite pilgrims near the city of Samarra, one of Iraq's worst in recent weeks, rose to 48 dead and 80 wounded, police and officials said on Sunday.
The bomber detonated an explosives vest on Saturday at a bus depot at the entry to Samarra, where Shi'ites gathered last week to commemorate the death of one of their 12 revered imams.
The attacker managed to infiltrate a crowd of pilgrims at a security checkpoint where authorities used explosives-sniffing dogs to search vehicles before they entered the city.
"From the cruelty I've seen, it's al Qaeda who carried out this terrorist attack. Al Qaeda insists on undermining stability and peace in Samarra," said Majeed Abbas, a local leader of the government-backed Sunni Sahwa militia.
While overall violence has dropped sharply in Iraq since the peak of sectarian warfare in 2006-7, security forces are fighting a weakened but still lethal insurgency and bombings and other attacks occur daily.
Attacks on Shi'ite pilgrims last month near the holy city of Kerbala killed dozens. At least seven people died and 78 were wounded by car bombs in the northern city of Kirkuk on Wednesday.
Samarra, 100 km (62 miles) north of Baghdad, is the home of the al-Askari mosque and shrine. Shi'ites gathered to mark the death of Hasan al-Askari, the 11th of the 12 imams.
Shi'ite religious events were banned under Sunni dictator Saddam Hussein, who was ousted in a US-led invasion in 2003. Shi'ite pilgrims have been frequent targets of insurgents since.
Local officials said most of the dead and wounded from Saturday's blast were transported to Baghdad overnight, with dozens of police and military vehicles escorting a convoy of ambulances from Samarra to the Iraqi capital.