The incident occurred on Sadulpur-Churu highway when the bus was stationed on the roadside after it developed some technical snag.
The speeding truck rammed into the bus leaving Tana Devi, Bhanvri Devi and Gita Devi dead.
The trio were inside the cabin of the bus, police said.
Four others were also injured.
Most of the passengers of the bus were standing outside it. The truck driver fled from the spot after the accident, the police said, adding the injured were being treated at a local hospital in Churu.
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