Berbatov scored twice and converted a late penalty, with Park Ji-Sung and Antonio Valencia adding United's other goals against the visitors who had Conor Sammon sent off late in the first half.
Chelsea's faltering title challenge suffered another blow when they were held 1-1 by neighbours Fulham in an early kick-off at Stamford Bridge, the home team registering their third successive league draw.
United's second successive 5-0 victory - they also thrashed Fulham by the same score - allowed them to halve their goal difference deficit on City who started the day with a plus-10 tally over their neighbours.
"Today's result pleases me considering the injuries we have had. We had 10 players missing and (defender) Jonny Evans was taken off at half-time," manager Sir Alex Ferguson told Sky Sports.
"In a close game I would have worried about that. We ended up with a back four that has never played together."
"Today was difficult," said City manager Roberto Mancini. "When you play a team who have all their players behind the ball at home, if you don't score in the first half it's not easy.
"It is impossible to score three or four goals in every game. There will be some moments in the year when you won't score."
"It was a patched-up team because we have so many players injured and then we lost our goalkeeper [Paul Robinson] but Mark Bunn came in and made some great saves," said Kean.
"We have got a very young team at the moment but we are digging in and... I thought my lads were exceptional."
