Pictured: The four surviving Barcelona terror cell suspects taken to court

They are accused of being part of a 12-strong cell led by a radical imam linked to the Madrid train bombings.

The four surviving suspects in the recent terror attacks in Spain appeared at the high court in Madrid on Tuesday 22 August. Mohamed Aallaa, 27, Driss Oukabir, 28, and Mohamed Houli Chemlal and Salah El Karib, both 34, were escorted to the courthouse by Spanish Civil Guards from a detention centre in Tres Cantos, near Madrid.

The four men are suspected of being involved in the killing of 15 people and injuring of many more in twin vehicle attacks in Barcelona and nearby seaside town Cambrils on 18 August. The investigating judge, Fernando Andreu, will decide what charges to press over the attacks. Those potential charges are expected to include counts of murder, terrorism, and possession of firearms.

The suspects are believed to be members of a terror cell from Ripoll, a town in northern Catalonia, where an imam linked to the deadly 2004 Madrid train bombings is thought to have radicalised the men.

After the attacks, police discovered the cell's bomb-making unit at a house in Alcanar, a town south of Barcelona, where they found 120 gas canisters and the remains of the Ripoll imam, Abdelbaki Es Satty.

Catalan police chief Josep Lluis Trapero said the cell was believed to be 12-strong and to have spent six months planning the attacks.

Five members of the alleged Ripoll cell were killed by police on Thursday 18 August. One police officer shot dead four of the terrorists who ploughed their car into pedestrians in Cambrils, killing one woman and injuring dozens.

The police's prime suspect, 22-year-old Moroccan national Younes Abouyaaqoub, was shot dead on Monday 21 August in Subirats, an area 25 miles (40km) west of Barcelona. He is believed to have been wearing a fake explosives belt and shouted "Allahu Akbar" ("God is Greatest") when police confronted him.

Oukabir, one of the surviving suspects, claims that he is innocent despite police discovering his passport in the van which ploughed into pedestrians on Barcelona's Las Ramblas. Oukabir says that his brother Moussa, who was killed by police in Cambrils, had stolen his documents.