TOKYO, Nov 23 (Reuters) - The operator of Japan's wrecked nuclear plant and three Mitsubishi group firms plan to build a new type of energy-efficient coal-fired power plants in Fukushima, a source said on Saturday.

Tokyo Electric Power Co will tie up with Mitsubishi Heavy Industries, Mitsubishi Corp and Mitsubishi Electric to build integrated gasification combined-cycle (IGCC) stations.

Mitsubishi group companies will have a majority of stake in the new plants while cash-strapped Tepco will be in charge of running the facilities, which they plan to put online around 2020, the source said.

Tepco has been under pressure to introduce energy-efficient facilities as all of its nuclear power plants have been closed since the Fukushima disaster, with no immediate prospects of restarting any nuclear plants given public distrust.

Mitsubishi Heavy also aims to be a leading player in the new IGCC technology, which will increase power output by 20 percent from conventional coal power plants, using the same amount of fuel.

Three reactors suffered core meltdowns at the Fukushima Daiichi plant north of Tokyo after the March 2011 earthquake and tsunami that triggered explosions and forced the evacuation of 160,000 people from nearby towns and villages.