Abdurahman Mohamed Farole, the president of Puntland, which declared its semi-autonomous status in 1998, condemned the killing as a "terrible incident".

"We are still investigating who was behind it," he said.

The deaths follow the killing of Puntland's information minister in Galkayo last week.

'Anti-Islamic' elements

The Pakistani preachers belonged to a Muslim group known as Tabligh, Sheikh Mohamed Abdi Said, a spokesman for the Ahlu Sunna religious group in the area, said.

The group "has never advocated violence" and the killings were "contrary to the teaching of Islam", he said.

Somalia's anti-government al-Shabab fighters - blamed by Ahlu Sunna for the deaths religious scholars, elders, traders and other opponents in the past - also condemned the murders.

"It is the worst thing in Somalia's history because the killing of religious men is unknown among the Somali community," Sheikh Ali Mohamoud Dhere, the group's spokesman, said in Mogadishu.

"This attack was carried out by anti-Islamic elements."

A report by the International Crisis Group released on Wednesday warned that if the regional government did not engage all of the semi-autonomous clans in the region, it "may break up violently, adding to the chaos in Somalia".