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.

A gang of gunmen disguised in military-style uniforms and carrying forged arrest warrants killed 25 police Monday, then hoisted the battle flag of al-Qaida in a carefully planned early morning shooting spree in western Iraq, officials said.

The killings in Haditha highlight al-Qaida's success in regaining a foothold in an area they once dominated through police executions and murdering city officials.

By going after police, the militants demonstrate to the residents of Haditha, a desert city closer to the Syrian border than to Baghdad, how isolated they are from the central government's protection and intimidate those who want to join the security forces.

The city's proximity to the border, just 65 miles away, means it is vital territory to al-Qaida if they want to ramp up operations in Syria to help overthrow the government of President Bashar Assad. Already, Sunni militants who revile Assad because he's a member of an offshoot religion of Shiism are crossing from Iraq into Syria.

The killings carried out by al-Qaida Monday morning demonstrated a high degree of coordination, knowledge of their targets and a boldness that indicated little fear of the local security forces ability to fight back.

The violence began with an attack on a suburban checkpoint around 2 a.m. in Haditha and ended with the gang disappearing into the desert a half hour later.

"We consider this attack as a serious security breach and we believe that al-Qaida or groups linked to it are behind this," said Mohammed Fathi, spokesman for the governor of Iraq's western Anbar province where Haditha is located.

Iraqi officials described a systematic plot to kill police in Haditha, 140 miles (220 kilometers) northwest of Baghdad, with attackers disguising themselves in military uniforms and driving cars painted to look like Iraqi interior ministry vehicles.

Fathi said the gang claimed they were military officials with arrest warrants for city police. They were stopped at a checkpoint outside Haditha, where they took away the guards' mobile phones before shooting nine of them, he said.

The gang's convoy, described by one Haditha police lieutenant as stretching 13 cars long, then stopped at the homes of two Haditha police commanders, including the colonel who served as the city's SWAT team leader. Brandishing the fake arrest warrants, the gunmen forced the commanders into the convoy, and shot both less than a quarter-mile (400 meters) away, Fathi said.