Six migrant workers, who were walking to their homes in Bihar from Punjab, were killed and four others seriously injured when a roadways bus ran over them on the Delhi-Saharanpur Highway in Uttar Pradesh's Muzaffarnagar district, officials said on Thursday.

The incident took place on the intervening night of Wednesday and Thursday between Ghalauli check-post and Rohana Toll Plaza, senior superintendent of police Abhishek Yadav said.

The bus driver has been arrested, the SSP said. Medical reports confirmed that the driver, Rajbir, was under the influence of alcohol at the time of the incident, station house officer Anil Kapervan said.

The Uttar Pradesh roadways bus was returning to Agra from Saharanpur after dropping migrant labourers to their homes.

A government official in Lucknow said Uttar Pradesh chief minister Yogi Adityanath expressed grief over the incident and announced an ex-gratia of Rs 2 lakh each to the families of the deceased migrants and Rs 50,000 to the seriously injured.

He has also asked the Sahranpur Commissioner to conduct an inquiry into the incident and fix responsibility, the spokesman said.

The chief minister has directed the officials to ensure proper treatment of the injured and arrangements for taking the bodies to Bihar, he added.

The deceased migrants were identified as Guddu (18) from Bhojpur, Virender Singh (28), a resident of Patna, Harek Singh (52), his son Vikas (22), Vasudev (22), Harish Sahni (42) -- all from Gopalganj, police said.

The injured were taken to hospital, they said.

The incident comes days after 16 migrant labourers, sleeping on railway lines, were crushed to death by a goods train in Aurangabad in Maharashtra on May 8.