A suicide bomber on Monday rammed a car packed with explosives into the entrance of the local government headquarters in Somalia’s capital Mogadishu, police and witnesses said.

“We are investigating for details and casualties,” Police Major Mohamed Nur told Reuters.

At least four persons reportedly died in the attack on the beleaguered city’s mayor office, several sources said. Many were also injured.

It is unclear who carried out the attack although Somali militant group al Shabaab has been waging an insurgency against the government and has claimed responsibility for similar attacks in the past.