It was Iraq's bloodiest day in nearly a month, and the scale of the coordinated explosions in more than a dozen cities showed an apparent determination by insurgents to prove that the government cannot keep the country safe ahead of the summit.

Iraq is due to host the meeting for the first time in 20 years and the government is anxious to show it can maintain security following the withdrawal of US troops in December.

"The goal of today's attacks was to present a negative image of the security situation in Iraq," government spokesman Ali Al-Dabbagh said. "Security efforts will be escalated to counteract terrorist groups' attacks and to fill loopholes used by them to infiltrate security, whether in Baghdad or other provinces."

Yesterday's deadliest incident occurred in the southern city of Kerbala, where twin explosions killed 13 people and wounded 48 during the morning rush hour, according to Jamal Mahdi, a Kerbala Health Department spokesman.

"The second explosion caused the biggest destruction. I saw body parts, fingers, hands thrown on the road," 23-year-old shop owner Murtadha Ali Kadhim said.  "The security forces are stupid because they always gather at the site of an explosion and then a second explosion occurs. They become a target." Blasts also struck in the capital, in Baiji, Baquba, Daquq, Dibis, Dhuluiya, Kirkuk, Mosul, Samarra, Tuz Khurmato and Dujail to the north, in Fallujah and Ramadi to the west, and Hilla, Latifiya, Mahmudiya and Mussayab to the south. Police defused bombs in Baquba, Fallujah and Mosul.

Most of the blasts targeted police checkpoints and patrols.

"This latest spate of attacks is very likely to have been co-ordinated by a large and well-organized group. It is likely an attempt to show the authorities that their security measures are insignificant," said John Drake, a senior risk consultant at AKE Group, which studies security in Iraq for corporate clients. Yesterday's attacks were the biggest since Feb. 23 when dozens of explosions across the country killed at least 60 people.

The Arab League summit on March 27-29 will be the first held in Baghdad since Saddam Hussein's invasion of Kuwait in 1990. Yesterday was also the day after the ninth anniversary of the start of the US invasion that toppled Saddam.

Security has been stepped up across the city's checkpoints, where thorough searches have backed up traffic for hours in recent days. In the northern city of Kirkuk, two car bombs exploded near a police headquarters, killing nine people and wounding 42, police and health sources said. In Baghdad, a car bomb killed four and wounded 11.

Police in Baquba said they had found and defused nine bombs, including one in a booby-trapped car which was parked on the road with a decapitated body.

By late afternoon, the toll from all the bombings compiled by Reuters fstood at 51 killed and 239 wounded.