TOKYO, April 10 (Reuters) - 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 megabanks Mitsubishi UFJ Financial Group, Sumitomo Mitsui Financial Group, Mizuho Financial Group, all 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...