35-year-old Indramani Shukla, a lawyer in the fray for the zilla panchayat elections, was shot dead on October 29 in Kotwali area of Pratapgarh while he was returning home in his car.
The accused identified as Tapan Mishra, Ankit Khandelwal, Ambrish alias Patta and Amit Kumar Tiwari were arrested with two pistols of .32 bore, a country-made pistol and a number of cartridges from Gaighat in the district, police said.
The accused were nabbed when they were allegedly planning to kill three persons, they said.
The STF is probing the matter, they added.