The incident occurred near village Ashrafpur under police station Shivratanganj on Lucknow-Varanasi national highway 56 when the truck hit the loader vehicle, a police official said.
All the four persons, including the driver of the loader, were killed, while the driver and the cleaner of the truck abandoned it and fled the spot, SHO Shivratanganj Mohammad Hamid said.
All the four persons were rushed to community health centre in Singhpur where the doctors declared them brought dead, he said.