Mogadishu, Somalia - At least 20 people were killed in a triple car bombing attack Monday in central Somalia, among them two local government officials. Witnesses said two vehicles loaded with explosives detonated in the morning, and a third in the afternoon.

The three explosions rocked the city of Beledweyne in central Somalia, killing at least 20 people and injuring dozens more.

Beledweyne police commissioner Bishar Hussein Jimale confirmed the attacks and the death of some local officials.

Jimale said the attacks were planned by al-Shabab, killing officials, civilians and soldiers. He said the victims including the deputy commissioner of finance in the Hiran region and MPs and ministers in Hirshabelle.

Jimale added that rescue operations were still in progress, working to find injured people who are trapped as well as to recover bodies.

"We mourn but we do not cry," he said in Somali, "and we will take revenge against al-Shabab."

The U.N. office in Somalia said in a tweet it condemned the attack and sent condolences to the families of the victims.

Two of the bomb attacks struck the Lama Galaay military base, which hosts the offices of the regional president and several local government officials.

One car bomb detonated near the entrance gate, then witnesses said a truck rushed toward the headquarters building and exploded. The third car bomb exploded while heading to the same target.

The attacks come barely a day after the Somali government announced the death of a senior al-Shabab commander identified as Abdulkadir Nadir in an airstrike in the Middle Juba region.

Nadir, who served as al-Shabab's finance chief was touted to replace the group's leader Ahmed Diriye, or Abu Ubaidah, who is reported to be sick. He had a $3 million bounty on his head from the U.S. government.

The Somali government described Nadir's killing as a 'thorn removed from the Somali nation."

The Somali government is involved in a major counterterrorism offensive against al-Shabab in the central regions of the country. The operation has gained the support of local tribal militias in Hiran and Galgaduud who have joined forces with federal and state government authorities.