At least 26 explosions struck cities and towns across Iraq on Tuesday, killing at least 49 people and wounding more than 200, despite a massive security clampdown ahead of next week's Arab League summit in Baghdad.

It was Iraq's bloodiest day in nearly a month, and the breadth of coordinated bombs 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 U.S. 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 told Reuters.

"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."

Tuesday's deadliest incident occurred in the southern Shi'ite Muslim holy 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 told Reuters.

"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 and Tuz Khurmato to the north, in Falluja and Ramadi to the west, and Hilla, Latifiya, Mahmudiya and Mussayab to the south. Police defused bombs in Baquba, Falluja 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-organised 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.

Army and police forces are frequently targeted in Iraq, where bombings and shootings still occur on a daily basis. Sunni Muslim insurgent groups say that despite the withdrawal of U.S. forces, they will not lay down arms and will continue to battle the Shi'ite-led government.

Although overall violence has declined since the height of sectarian fighting in 2006 and 2007, Iraqis worry whether their government has the wherewithal to impose security nine years after the U.S.-led invasion that overthrew Saddam Hussein.