Mogadishu: Two people holding British passports were among four killed during a rebel attack at a Somali school, witnesses said on Monday.

A spokesman for the Islamist rebels confirmed the killing in the central town of Beledweyne in Somalia's Hiraan region but denied responsibility.

"Al Shaabab fighters entered the town and suddenly attacked houses of government officials," said, Ahmed Elmi, a resident.

"Then they attacked a school where they killed two Kenyans, a British woman and a Somali man with a British passport," Elmi said. 

In a separate attack, four people were killed and 16 were wounded when gunmen threw a grenade into a cinema in the southern town of Merka.