NEW DELHI, October 6: An 18-year-old youth was stabbed to death by unidentified assailants outside his Bawana residence in north-west Delhi yesterday evening. Riyaz was apparently returning home after buying vegetables at a nearby market when he was stabbed thrice by the assailants. In another case, Wahid (20) was reportedly stabbed by four youths inside a moving bus in the Anand Parvat area yesterday evening. One of the assailants, Sanjeev (22), has been arrested.The police say that the youths asked Wahid to make way for them inside the crowded bus. Suspecting them to be pickpockets, Wahid warned the other passengers. This reportedly angered the youths and they stabbed him repeatedly.