Unidentified gunmen shot dead a senior official of the Somali rebel group Hizbul Islam in Mogadishu's main market today, sparking several revenge killings, officials and witnesses said.

Hizbul Islam has often fought side-by-side with the more hardline al Shabaab rebels against government forces in a drive to topple Somalia's Western-backed administration. But a battle for control of the lucrative southern port of Kismayu has pitted the two groups against each other.

"One of our senior officials, Bare Ali Bare, was assassinated in Bakara today," Hizbul Islam spokesperson Sheikh Mohamed told reporters. "He tried to defend himself but his pistol ran out of bullets and he was killed on the spot. We do not really know who killed him."

A witness said he saw two masked men shooting at Bare. "It is only al Shabaab and Hizbul Islam that can kill people in Bakara market. He was previously attacked in his room with grenades and we all anticipated he would one day fall into the hands of al Shabaab," witness Zakarie Hussein.

The killing sparked further shootings in which four people died, witnesses said.

In a separate incident, three people died and four others were wounded when Islamists attacked government troops who were fighting each other on a road not far from the presidential palace, according to Ali Yasin Gedi, vice chairperson of the human rights group Elman. - Reuters