The ghastly incident took place in Ghurpur police station area of the district's trans-Yamuna region, about 40 kms from the city, on Thursday morning.
"The girl was picked up from her house in Amreha Budawan village while she was asleep besides her mother. She was brought back home by villagers who found her lying in a pool of blood in the nearby fields, where the assailants appear to have dumped her after the sexual assault," Sandeep Tiwari, Public Relations Officer of the Senior Superintendent of Police of Allahabad, said.
"A case has been registered against unknown persons under relevant sections of the Indian Penal Code. Four suspects have also been arrested for interrogation," Tiwari said.
SSP Anand Kulkarni also visited the site of the crime today, he added.