The administration imposed Section 144 of the CrPC in Barhaj area of Deoria district after a 25-year-old man was allegedly beaten to death by some youths on Janmashtami.
Section 144 of the CrPC prohibits the assembly of more than four persons in an area.
District Magistrate Amit Kishor said the restrictions would remain in force till September 15.
Sumit was injured when he tried to save his father from the attackers, who were enraged over the objection to loud music during the festival.
The incident had taken place on Saturday night in Barhaj's Patel Nagar, police said.
"On the occasion of Krishna Janmashtami, some youths were playing DJ in Patel Nagar of Barhaj on Saturday night. Munnu Lal asked them to stop it, which enraged 10-12 youths," Deoria SP Shripati Mishra said.
"They attacked Munnu Lal with sticks. When his sons Sumit and Sachin, along with his wife Sanju Devi, rushed to save him from the attackers, they too were beaten up," the SP added.
On getting information, police rushed to the spot and admitted the injured to the local health centre, where doctors referred Munnu Lal and Sumit to the district hospital for treatment.
Sumit (25) was declared dead by the doctors at the district hospital, the SP said, adding the hunt was on to nab the culprits.
