Croatia defender Vedran Corluka doubled their lead with his first goal of the season, giving Belenov no chance with a firm header after Alexander Samedov's clever assist midway through the first half.
Morocco midfielder Mbark Mboussoufa put the issue beyond doubt, making it 3-0 in the 31st minute with Maicon, who was booked for diving early in the second half, turning provider.
Djibril Cisse got a consolation for the home side, who are ninth in the table, in added time, rising above the Lokomotiv defence to head home from Bulgaria captain Ivelin Popov's right-wing cross.
Lokomotiv's Belarussian coach Leonid Kuchuk returned to the Kuban Stadium for the first time since June when he suddenly left the Krasnodar-based side after guiding them to the Europa League to take over the Moscow club.
Lokomotiv top the standings with 39 points from 18 matches, two points ahead of Zenit St Petersburg, who drew 1-1 at lowly Terek Grozny on Sunday.
Earlier on Monday, champions CSKA Moscow only managed a goalless draw at Rostov to remain fourth on 34 points, two behind city rivals Spartak, who thrashed FC Volga Nizhny Novgorod 6-1.