Lucknow: Two policemen were killed Wednesday in Sambhal district as unidentified assailants opened fire at a jail van and helped three undertrials escape from the custody. Sambhal Superintendent of Police Yamuna Prasad said two constables, escorting some undertrial prisoners to Moradabad, were shot dead day by heavily armed criminals in an audacious attack on the police team. The incident took place at Dhannumal crossing near Banither village in the district when a police van returning with 24 undertrials prisoners to Moradabad after hearings in a Chandausi court was attacked by some persons, said Additional DG (Law and Order) P V Ramashastri. The deceased constables were identified as Harendra and Brijpal. Attempts are on to nab the culprits, Ramashastri said.