At least 18 people were killed and 19 others injured after the bus - they were travelling in - collided with another vehicle in Uttar Pradesh's Unnao on Wednesday.
Three women and one child were among those killed in the accident, the police said.
The double-decker bus was travelling from Bihar's Sitamarhi to Delhi when it rammed the milk tanker from the back on the Lucknow-Agra expressway in the morning, reports NDTV.
The impact of the collision was so huge that the people were flung out of the vehicle, the police said. Visuals from the scene showed bodies on the ground, twisted scraps of metal, shattered glass and destroyed belongings.
"Today at around 5:15 am, a private bus coming from Motihari, Bihar, collided with a milk tanker. Eighteen people have lost their lives, and 19 others are injured in the accident, said Gaurang Rathi, District Magistrate, Unnao.
The injured have been rushed to a hospital and are being treated there, officials said.
Chief Minister Yogi Adityanath has expressed anguish over the tragedy and directed the officials to ensure proper treatment of the injured, his office said.
Prime Minister Narendra Modi has announced a compensation of ₹ two lakh for the dead and ₹ 50,000 for those injured in the accident, his office said on X - earlier known as Twitter.
President Droupadi Murmu has also condoled the loss of lives. "The news of the death of many people in a road accident on the Lucknow-Agra Expressway in Unnao, Uttar Pradesh is extremely sad. I express my deepest condolences to the family members of those who have become victims of such sudden death and wish for the speedy recovery of those injured," Ms Murmu said in a post on X in Hindi.
