Delhi Police has detained 12 persons suspected to be linked with a terror outfit planning an attack in the city and recovered explosives from their possession after a series of overnight raids in the national capital and neighbouring states. The ongoing raids are part of a joint operation of Delhi Police and a central intelligence agency. A team of the force's anti-terror unit Special Cell zeroed in on two of the youths, while they were allegedly in the process of making improvised explosive device, from east Delhi's Gokulpuri area. The names of the others emerged during their questioning and they were tracked down one after another in the wee hours of Wednesday, a senior official said. All of them are suspected to be members of a sleeper unit of a terror outfit, planning an attack in the national capital and other cities, the official said. Special Cell teams are conducting raids in Delhi and UP, and several arrests are likely in the next 24 hours. Explosives have also been recovered from their possession. The 12 are being questioned by Special Cell sleuths and intelligence officials. Investigation is underway, the senior official added.