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