London - A 22-year-old Muslim convert who attempted to detonate an explosive device made of nails and chemicals in a busy restaurant was on a 'suicide mission,' police in the university town of Exeter in south-west Britain said Friday. Nicky Reilly was arrested Thursday at the Giraffe restaurant, where families were dining, after one of the two devices he had taken into the lavatory partially exploded, injuring his face. Two more men were arrested Friday in Plymouth, the nearby port city where Reilly lived, police said. They also said Reilly had been 'known' to the intelligence services before the planned Exeter attack. Police sources said Friday that the bombs were 'viable' devices made of chemicals, strips of aluminium foil and nails. Moments before leaving his home in Plymouth, Reilly had received a text message of 'encouragement' for the failed suicide mission. He carried the fireball-type devices, which were volatile and could have exploded on shaking, on a bus from Plymouth to Exeter which had more than 50 passengers on board. The Giraffe restaurant in Exeter city centre was packed with families at lunchtime Thursday, when Reilly planned to carry out the attack. A police spokesman said that Reilly, who has a history of mental illness, had professed the Muslim faith which he had adopted. 'We believe, despite his weak and vulnerable state, he was preyed upon, radicalized and taken advantage of,' a police spokesman said.