A coalition of climate groups are stepping up pressure on Japan's top three banks to cut financing linked to fossil fuels, filing shareholder resolutions to be voted on at the companies' annual general meetings in June, sources said on Monday.

The groups are targeting mega-banks Mitsubishi UFJ Financial Group, Sumitomo Mitsui Financial Group and Mizuho Financial Group, all of which are key to financing oil and gas projects, said the sources, who declined to be identified as the information is not yet public.

The coordinated effort marks a step up from the past three years, when climate groups targeted one mega-bank each year, as they are now calling simultaneously for action by the Japanese banks, which are seen as lagging their global peers in efforts to slash carbon emissions.