Twin suicide car bombings killed at least 18 people, including the two attackers, in northern Somalia on Sunday, officials said.
A truck loaded with explosives drove into an administrative compound in Galkayo, about 750 kilometres north of Mogadishu, Mayor Yasin Tumey said. Survivor Liban Ali compared the powerful blast to an earthquake.
Another suicide car bombing then ripped through the same area as people were trying to help the victims of the first blast.
The dead included a local police commander and his deputy, five soldiers, as well as people at a nearby market, according to the mayor and local media reports.
Tumey said at least 20 other people were injured. Several of them were in critical condition, according to a medical source who did not want to be named.
The explosions caused several buildings to collapse, witnesses said.
The Islamist group al-Shabaab claimed the attack - one of its bloodiest in the region - on pro-insurgent radio Andalus.
Security official Mohamed Hasan said the group wanted to compensate for its recent military losses in the south by taking its campaign to relatively peaceful areas in the north.
Analysts said al-Shabaab could also be seeking revenge for the arrests of five of its members in Galkayo last week.