An alert has been sounded in the Eastern and East Central Railway (ECR) zones after intelligence inputs suggested entry of Taliban-trained suicide squads into Bihar and in metropolises like Kolkata , official sources said on Monday. Senior Divisional Security Commissioner of the Railway Protection Force of East Central Railway NK Sinha in a note to superintendents of railway police in Bihar , informed of the inputs suggesting infiltration by suicide squads into Bihar and metropolitan cities including Kolkata , they said. "We have sounded an alert and special attention is being paid to guard vital installations in the wake of the inputs about possible attacks by Taliban-trained suicide squads," they said. The copies of the letter were available with superintendents of Indian railway police at Patna, Bhojpur, Buxar, Jehanabad, Nawada, Gaya, Nalanda, Lakhisarai, Jamui and Begusarai.