At least two police officers have been wounded in the Somali capital Mogadishu after a car bomb exploded next to a police department building in an attack claimed by the insurgent al-Shabab group.

Police said the bomb went off on Friday after they had arrested the driver of a car suspected of carrying explosives.

Officers said they were waiting outside the criminal investigations department for bomb disposal experts when the explosives in the car detonated.

The attack was the latest in a wave of assaults in war-torn Mogadishu.
   
"We had seized this car earlier in the morning and detained the driver, who is alive and under arrest," Mohamed Ali, a police officer, said. "It went off prematurely as we were waiting for bomb experts to come and disarm the car."

The blast destroyed the gate to the police department and shattered the windows of buildings nearby. The explosion set ablaze cars parked in the compound, residents said.

The criminal investigations department is located near other government offices in central Mogadishu.

Shabab claims responsibility

Al-Shabab, which is allged to have ties to al-Qaeda, claimed responsibility for the blast in a post on Twitter. They said the car bomb was triggered remotely by their mujahideen, or holy warriors.

"The mujahideens managed to get a car bomb into the complex before exploding it remotely 30 minutes later," the group said in its online message.
   
Al-Shabab aim to overthrow Somalia's weak leaders and institute Islamic rule. They have been fighting the Transitional Federal Government since 2007. Their online posts went on to say that al-Shabab would be embarking a "new campaign" to target bases associated with the TFG and any foreign governments.
    
The group has intensified the frequency of attacks in Mogadishu since withdrawing from most of its bases in the capital in August last year.

"This is happening because al-Shabab are able to hide themselves with people returning back to Mogadishu," Colonel Omar Mohamed, of the police's criminal investigations department, told Al Jazeera shortly after the attack.

Al-Shabab fighters control large parts of central and southern Somalia, but are facing increasing pressure from regional armies, including Kenyan troops in the south and Ethiopia's army in the south and west.

Thousands of Somalis are fleeing into the capital after African Union-backed government troops have launched renewed attacks on Shabab positions on the outskirts of the capital.

More than 7,200 people have fled into the city from the rebel-held Afgoye corridor, a 40 kilometre (25-mile) stretch of makeshift camps along a road, home to some 410,000 people, the UN refugee agency said on Friday.

"UNHCR fears for the safety of the displaced and we urge all armed groups and forces to make the protection of civilians a priority," the agency said.