Four successive blasts hit the Iraqi city of Kerbala on Sunday, killing at least 16 people and wounding dozens more as they lined up outside a local government building.
The first bomb ripped through a crowd of guards and civilians gathered in front of an office issuing ID cards and passports, and three other explosions went off shortly after as emergency services arrived at the site, police said.
Panicked security guards fired shots in the air to keep onlookers away after the blasts tore the front off nearby buildings and set ablaze cars parked on the street.
"I was inside my house when I heard a big explosion. When I got out I saw many people wounded and some bodies on the ground," said Mohammed Na'eim, a local resident.
A Kerbala police official said 16 people were killed and 34 more wounded while a Kerbala health department official said so far hospitals had 10 dead and another 110 wounded.
Violence has in Iraq has eased since the height of sectarian strife in 2006-2007, but insurgents tied to al-Qaeda and Shi'ite militias still carry out daily attacks as US troops prepare to withdraw at the end of this year.
Kerbala, a major Shi'ite holy city 80km (50 miles) southwest of Baghdad, has often been attacked in the past by Sunni Islamist insurgents targeting Shi'ite pilgrims who flock to the city's religious sites.
A suicide bomber targeting pilgrims on their way to Kerbala killed four people and wounded 17 on Thursday.
Insurgents this year have increasingly targeted local government buildings and the security forces in an attempt to destabilise Iraq's fragile government that is formed from Sunni, Shi'ite and Kurdish political blocs.
Bombers frequently set off one blast and trigger more when security officials arrive to help casualties.
More than eight years after the US invasion that toppled Saddam Hussein, the remaining American soldiers are scheduled to withdraw from Iraq at the end of this year when a bilateral security agreement with the OPEC oil producer ends.
US troop numbers in Iraq will have dropped to around 30,000 by the end of this month. They are mostly involved in advising and assisting Iraqi forces since ending combat missions last year.
Iraqi and US officials say local armed forces can contain the country's stubborn insurgency, but many Iraqis see some remaining American military presence as a guarantee of stability as their country works to rebuild from the war.
Prime Minister Nuri al-Maliki's government is in talks with US officials over whether some American troops will remain on as trainers after 2011, but those negotiations are still in the preliminary stages.
