Twin bombings at a Roman Catholic cathedral in the Philippines have killed at least 20 people attending Sunday service and wounded dozens more, in one of the deadliest attacks to hit the region in recent years.

The first blast went off inside the cathedral on Jolo island, in Sulu province, shattering the building’s windows and destroying its entrance.

Security forces rushed to the scene, only for the second bomb to be detonated outside, officials said.

The second explosion hurled debris and the remains of victims across a town square immediately outside the cathedral.

Five soldiers died in the attack, with 65 civilians also left wounded.

Pictures showed several rows of wooden pews destroyed inside the cathedral, with wreckage strewn across a blackened floor.

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Bodies were photographed on the busy street outside, which was sealed off by troops as vehicles transported the dead and wounded to the hospital.

Humvees and army trucks could also be seen at the scene.

There was no immediate claim of responsibility, but police suspect the bombings were the work of the Abu Sayyaf, a militant group that has pledged allegiance to Isis.

Jolo island is a stronghold for the Abu Sayyaf, and successive administrations have failed to prevent the militants from running a lucrative piracy and kidnapping operation from the region.

“The enemies of the state have boldly challenged the capability of the government to secure the safety of the citizenry in that region,” a spokesperson for Rodrigo Duterte, the nation’s leader, said.

“The armed forces of the Philippines will rise to the challenge and crush these godless criminals.”

The attack comes six days after the mainly Muslim area overwhelmingly voted “yes” in a referendum on the region’s autonomy.

But most voters in Sulu province, where Jolo is located, rejected it, setting the stage for further political turmoil in the area.

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Delfin Lorenzana, the defence secratary, called the attack a “dastardly act” and urged the local population to cooperate and “deny terrorism any victory”.

“We will not allow them to spoil the preference of the people for peace,” said Hermogenes Espero, the country’s national security adviser.

A Catholic bishop, Benjamin de Jesus, was gunned down by suspected militants outside the same cathedral in 1997.