POLICE have found a belt with real explosives at the house where the terror suspects accused of killing 15 people in attacks on Barcelona and Cambrils last week had allegedly been preparing a bigger attack.

Six of the attackers shot dead by police were wearing fake suicide belts.

A police spokesman said yesterday the belt with viable explosives was found at a house in Alcanar, south of Barcelona, where two other cell members died in an explosion last Wednesday prior to the attacks.

Police had already found more than 100 tanks of butane gas and materials to make TATP, an explosive used by Daesh militants, at the house.

Chief investigating magistrate Fernando Andreu provisionally jailed two of the four surviving alleged cell members on Tuesday after hearing testimony in the National Court in Madrid that the group had been preparing massive bombs for an imam who planned to blow himself up at a Barcelona monument.

It was not immediately clear if the belt found amid remains of the blast in Alcanar was meant to be used by the imam, Abdelbaki Es Satty, who allegedly masterminded the attacks and recruited the others in the cell, according to the testimony by the two jailed survivors.

The two — Mohamed Houli Chemlal, 21, and Driss Oukabir, 28 — identified Es Satty as the ideological leader of the cell, according to a Spanish judicial official who attended the proceeding.

Investigators believe Houli Chemlal is key to shedding further light on the imam’s role and plans as the only survivor in the blast in Alcanar where Es Satty and another cell member died last Wednesday, the official said.

Houli Chemlal was arrested in a hospital after surviving the blast.

He told the court he was alive because he was on the outside porch of the house washing dishes after dinner.

A regional police spokeswoman said investigators are also looking into material found during searches late on Tuesday at a cyber cafe in Ripoll and a house in Vilafranca del Penede. She said the operation was continuing.