Two explosions hit Uganda's capital Kampala on Tuesday, injuring some people in what police termed "an attack" on the city, the latest in a string of blasts targeting the country.

"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 AFP.

"The explosions took place near the Central Police Station and another took place near the entrance to Parliament, all in the central business district," he said, adding that the injured had been taken to hospital.

The explosion near the police station shattered windows while the one near the entrance to parliament saw cars parked nearby burst into flames, he added.

"We have dispatched a team" to the area, Uganda Red Cross spokeswoman Irene Nakasiita told AFP.

Kyle Spencer, the executive director of Uganda's Internet Exchange Point, who heard the blasts, told AFP that the explosions had sparked panic among many people nearby.

"The road to parliament is closed off, there are people just crying, everyone else is just trying to get away from these areas," he said.

"Everybody is evacuating office buildings and the buildings are locking up and not letting anybody inside."

Parliament cancelled its Tuesday session following the attacks, asking members to avoid the area "as security forces are working hard to restore order".

The attacks follow two blasts last month -- a bus explosion near Kampala that wounded many people and a bombing at a roadside eatery in the capital that killed one woman.

Police said last month both those attacks were connected and carried out by the the Allied Democratic Forces (ADF). They also warned that extremists were believed to be plotting a major new attack.

The ADF, historically a Ugandan rebel group, has been accused of killing thousands of civilians in eastern Democratic Republic of Congo (DRC). In March the United States officially linked the ADF to the Islamic State group.