President Rodrigo Duterte visited the southern Philippines where twin bomb blasts at a Roman Catholic cathedral killed at least 20 people and wounded more than 100.

Duterte met top defence, military and police officials inside the Cathedral of Our Lady of Mount Carmel in Jolo, Sulu province, before proceeding to a mass wake for victims of the bombing, according to photos posted by a former senior aide of the president.  

Before Duterte's visit on Monday, Oscar Albayalde, the country's police chief revealed that the brother of a slain Abu Sayyaf leader is a suspect in the attack on Jolo, an island in Sulu province in the restive south.

He identified the person by his alias, Kamah, brother of Abu Sayyaf leader Surakah Ingog. The suspect, who the police said is a known bomb-maker, was caught on security camera footage near the church shortly before the attack. Kamah is still at large, the police chief said, adding that about 4kg of explosives were used in the bombing.

The attack came six days after a referendum on expanded autonomy for the mainly Muslim region returned an overwhelming "yes" vote amid hopes the plan would bring development, jobs and peace to a region long plagued by poverty and instability.