MANILA- The leadership of the Catholic Church in the Philippines called on both Christians and Muslims to work together against violent extremism in Mindanao following a church bombing in Jolo, Sulu.

Catholic Bishops' Conference of the Philippines (CBCP) President and Davao Archbishop Romulo Valles called on "all religions of peace" to join hands in the fight against terrorism.

"[W]e ask our Christian brethren to join hands with all peace-loving Muslim and Indigenous People communities in the advocacy against violent extremism," he said in a statement.

"May all our religions of peace guide us in our quest for a brighter future for the peoples of Mindanao," he added.

At least 20 people were killed while over 100 others were wounded in a double bomb attack in a Catholic Church in Jolo, Sulu. The Islamic State has claimed responsibility for the attack.

• IN PHOTOS: Bloody Sunday bombing in Jolo

The Philippine National Police however suspect that the blast was a handiwork of an Alias Kamah, alleged brother of slain Abu Sayyaf group leader Surakah Ingog.

The bombings came a week after a regional plebiscite to approve a law that will grant wider self-rule to the Muslim minority in the south.

Sulu, the province that includes Jolo, voted against ratifying the Bangsamoro Organic Law.

Valles also condoled with families of the victims and condemned the terrorist attack.

"We condole with the families of the several soldiers and civilians who were killed by the explosions," he said. "At the same time, we condemn this act of terrorism that has taken place only a few days after the plebiscite on the Bangsamoro Organic Law."

Jolo apostolic administrator, Fr. Romeo Saniel meanwhile called for justice for the victims of the blasts as he mourned the death of his friends.

“They bravely stayed in Jolo in spite of the threats and insecurities. I believe they have died for their Christian faith,” Saniel was quoted in a CBCP News report.

“No words can describe the sorrow and pain that we feel these days. May they be given justice in God’s time,” he added.

On Sunday, Pope Francis condemned the twin Church bombings and prayed that God would convert the hearts of the perpetrators.

Francis, who was in Panama for a visit, expressed his "firm condemnation of this act of violence that causes more mourning in the Christian community. I pray for the dead and the injured. May the Lord, prince of peace, convert the hearts of the violent ones."

-with a report from Reuters

• Pope, world leaders condemn 'terror' attack on Jolo church