Two explosions hit the center of the Ugandan capital Kampala early on Tuesday, killing at least three people. The two blasts took place in the central business district — one near the Central Police Station and a second near the entrance to Parliament.

Reports claim that three attackers on motorbikes blew themselves up near parliament and the city’s police headquarters. NTV Uganda said 27 people have been hospitalized with injuries, adding that the 27 include police officers.

“First responders included Red Cross personnel who were using fire extinguishers to curb the fire on Parliamentary Avenue,” the station said on Twitter.

The unsolved murder of the young African boy whose torso was dumped in the Thames 20 yrs ago

The cause of the blasts remains unclear. “What we can say (is) this was an attack but who is responsible is a matter that is under investigation,” Uganda’s Assistant Inspector General of police Edward Ochom told the AFP news agency.

Some lawmakers were seen evacuating the precincts of the parliamentary building nearby, national broadcaster UBC reported. Proceedings in parliament have been called off and lawmakers have been asked not to come to the building.

Security officers have also deployed sniffer dogs to search for evidence around the sites of the blasts. No group has claimed responsibility for the blasts, but the police said the attacks were carried out by a “domestic terror group” linked to the Allied Democratic Forces (ADF). The ADF was formed in the late 1990s in opposition to Uganda’s long-serving leader Yoweri Museveni, according to BBC.

Ugandan soldiers are part of an African Union peacekeeping force in Somalia fighting al Shabaab, an insurgent group allied to al-Qaeda. Al Shabaab has carried out several deadly bombings in Uganda. Last month, the Islamic State group said it was responsible for an attack on a bar in the Ugandan capital which killed a waitress.

That same month, Ugandan police said a suicide bomber had exploded on a bus, killing himself and injuring others.