A female suicide bomber has killed at least 42 people and injured 58 in the Shia Iraqi holy city of Karbala, Iraqi health officials say.
Pools of blood could be seen at the site of the explosion
The bomb went off near the Imam Hussein shrine, reportedly inside a cafe, and eyewitnesses described seeing bodies scattered across the street.
Seven Iranians are believed to be among the dead, health officials say.
The city has seen deadly bomb attacks in the past, with about 100 people killed in two blasts last April.
Officials suspect al-Qaeda insurgents were behind the bombing in the city 80km (50 miles) south of Baghdad, but no group has claimed responsibility.
In the Iraqi capital Baghdad, a mortar attack by unidentified insurgents killed five people and wounded seven on a football pitch.
Earlier in the day, bombs in and around the city killed at least two Iraqi civilians and two US soldiers.
The attacks came during an official visit to Iraq by the US Vice-President, Dick Cheney.
'Smoke and bodies'
The bomb went off in a cafe for day labourers, Reuters news agency reports.
BOMB ATTACKS ON KARBALA
17 March 08: Female suicide bomber kills 42, injures 58
28 April 07: Car bomb kills 55, injures about 70
14 April 07: Suicide bomber kills 42, injures at least 150
5 January 06: Suicide bomber kills 60, injures more than 100
2 March 04: Bombs kill at least 85, injure 230
"I was talking with a friend and eating bread a few metres away from the cafe and I suddenly heard a huge explosion and I was thrown to the floor," Mohammed Kadhem, 39, was quoted as saying.
"I saw smoke and bodies."
Hassan Khazim, 36, who was wounded in the face, told the Associated Press he had seen "bodies flying in the air".
"All the tight security measures designed to protect us were in vain," he said.
As a city holy to Shia Muslims, Karbala attracts pilgrims from neighbouring Shia-majority Iran, as well as the mainly Shia south of Iraq.
Aqeel Khazali, governor of Karbala province, confirmed the bomber had been a woman but gave few other details.
On 28 April of last year, a car bomb killed at least 55 people and injured about 70 in Karbala, two weeks after a suicide bomber killed at least 42 people in the city.
Monday's attack would seem to be an act calculated to provoke Iraqi Shia Muslims at a time when one of the country's largest Shia militias, the Mehdi army, has declared a ceasefire and reigned in its fighters, the BBC's Adam Brookes reports.
But it would seem to continue an increase in violence noticeable in the last few weeks, our correspondent says.
Mr Cheney was paying a flying visit to Baghdad.
He met senior Shia leaders and said that Iraq's people had the unwavering support of the US as they consolidated their democracy.