An unidentified assailant today stabbed to deaththree passengers and injured one seriously while they were sleeping in a bus inAndhra Pradesh's Nellore district, police said.
The incident took place on the outskirts of Thada town ataround 4 AM.
The assailant started attacking sleeping passengers,travelling in a state-run bus en route Chennai from Bhadrachalam of Khammamdistrict, with a knife, police said.
While three passengers died on the spot, another wasinjured, a senior police officer said.
The accused fled the scene after the incident.
"The identification of the assailant and the motivebehind the attack was yet to be established. Teams are on the look out of theaccused," the police officer said.