Dempo, who led 2-0 at half time, scored through Joaquim Abranches (5th), Clifford Miranda (35th, 77th), Sakibo (56th, 59th, injury time) and Joy Ferrao (84th).
The win takes Dempo to 33 points from 16 matches, same as East Bengal who lost today against Churchill Brothers while United Sikkim FC remained at the bottom with 10 points from 16 matches.
Dempo, who had failed to win in their last three matches, were desperate to garner full points to keep themselves close to Churchill Brothers who are leading the table with 37 points.
They started aggressively and never felt the absence of their key players who were on the injury list and took the lead in the fifth minute when Abranches accepted a pass from Godwin Franco to fire the ball into the net.
The goal put the rival defence in disarray as Dempo piled on the pressure and after coming close on few occasions increased the lead in the 35th minute through Miranda who found the net off a Sakibo pass to have the home side leading 2-0 at half time.
United Sikkim goalkeeper Ghosh put up a brave fight as he made couple of good saves in the second half as the home team came up with a barrage of moves and the United Sikkim defence crumbled under pressure to concede five more goals.
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Miranda laid a pass to Sakibo who found the net from close in the 56th minute. Three minutes later, Sakibo again found the net when he flicked the ball above the visitors keeper Ghosh off a pass from Godwin Franco.
Sakibo then laid a pass to Miranda who scored his second goal in the 77th minute while substitute Joy Ferrao found the target in the 84th minute. Sakibo scored his third goal in the injury time.