TOKYO (Reuters) - Fishermen working off Japan's destroyed Fukushima nuclear plant have agreed to allow the release of uncontaminated groundwater around the facility into the ocean, Jiji news agency reported on Tuesday, in a rare victory for the site's operator.

Tokyo Electric Power Co (Tepco), the operator of the Fukushima station that suffered triple nuclear meltdowns after the March 2011 earthquake and tsunami, has been lobbying local fishermen to allow a "groundwater bypass" for nearly two years.

A ban on fishing after the nuclear accident pushed most fishermen in Fukushima out of a job except for occasional work catching certain types of fish deemed safe.

Tepco's bypass will release 100 metric tons of groundwater a day that flows downhill towards the devastated plant. The water will be funneled to the sea before it becomes contaminated by flowing into the wrecked reactor basements. Around 400 metric tons of groundwater flows into reactor buildings each day.

Local fisheries unions had been bitterly opposed to the utility's bypass after irradiated water leaked from tanks that were just uphill of the proposed groundwater drains last year. The leaks sparked international alarm and led to a boycott of Fukushima fish by South Korea.

Last month Tepco found another leak of highly contaminated water from one of its hastily built tanks at the plant.

In response to the leaks, Japan pledged half a billion dollars to build a wall of ice circling the plant and upgrade Tepco's faltering water treatment system. There are roughly a thousand tanks at the Fukushima plant holding more than 431,000 metric tons of radioactive water.

(Reporting by Mari Saito; Editing by Jeremy Laurence)