Twelve security agents have been killed by a roadside bomb planted outside a Somali town where political leaders have been meeting to try to resolve a row over a presidential selection process due to be held on Monday.

Militant group Al Shabab, which analysts say is keen on exploiting the deadlock, claimed responsibility for Sunday's attack.

READ MORE: Militant group attacks hotel in Somalia’s Mogadishu

Those killed included Abdirashid Abdunur, the head of the National Intelligence and Security Agency in Dhusamareb town, police officer Mohamed Ahmed said. 

In all, 12 people from the agency were killed in the attack near the town, police said.

READ MORE: Al Shabaab has created a perfect storm in Somalia

Political crisis 

A deal on how to choose a new president on Monday has been elusive so far, threatening to unleash more political turmoil.

Somalia had initially aimed to hold its first direct election in more than three decades but delays in preparations, and the government's inability to rein in daily attacks by al Qaeda-linked Al Shabab insurgents, meant switching to an indirect vote, with elders picking lawmakers who would choose a president.

However, regional authorities in at least two of Somalia's five federal states, Puntland and Jubbaland, oppose holding the election for now.

READ MORE:Somalia's politicians fail to reach deal on elections