Explosions rocked two of Somalia's largest cities on Saturday as officials said a suicide car bomber detonated near the port in Mogadishu, the nation's capital, and a land mine in a restaurant on the outskirts of Baidoa, the southwestern Bay region, killed five people.

Early on Saturday in Mogadishu, a suicide car bomber drove into a checkpoint just outside the port.

"Metal debris fell all over us inside the port, and we heard gunfire," a port worker who witnessed the attack told Reuters. "Security forces have surrounded the area.”

The bomber sped through the first security checkpoint before police officers opened fire at the vehicle which exploded outside the gates, Ismail Mukhtar, spokesman for Somalia's information ministry, told The Associated Press.

The bomber driving the car is reported to have tried to hit a police post in front of the port before the explosion, according to the BBC.

Two police officers and five passersby were injured while the bomber died in the attack.

In Baidoa, a land mine detonated near a restaurant on the outskirts of the city as people were dining during the morning rush, killing five people and wounding 10 others, an official in the Southwestern regional state told The Associated Press.

Militant group al-Shabab said it was behind both incidents, according to the BBC.

The militants, allied to al-Qaeda, said they were targeting tax collectors meeting at the restaurant and soldiers in Baidoa.

The attacks which come 11 days after the Shabab claimed responsibility for a suicide bombing on a Turkish military base in Somalia and are the latest examples of the chronic failure of the country's security sector to crack down on terrorist groups.

Somalia has been mired in conflict since 1991, when clan warlords overthrew dictator Siad Barre and then turned on each other.

Since 2008, the Islamist militant group al Shabaab has been fighting to overthrow the central government and establish its rule based on its own harsh interpretation of Islam's sharia law.

(With input from agencies)