MANILA, March 21 (Reuters) - A leaking fuel tanker that sank off the central Philippines three weeks ago has been found using an underwater robot from Japan, a provincial governor said on Tuesday, as authorities sought more foreign help to address the oil spill.

The discovery of MT Princess Empress, which was carrying about 800,000 litres (211,338 gallons) of industrial fuel oil when it capsized on Feb. 28 and eventually sank, was deemed crucial in stopping the spill, which reached shorelines in three provinces.

Plugging the leaks and extracting any remaining oil from the tanker was urgent, Oriental Mindoro Governor Humerlito Dolor said in a media briefing.

With the help of a remotely-operated vehicle that arrived on Monday from Japan, Dolor shared the first photos of the Philippine-flagged vessel from its exact location. The robot will also help determine the tanker's condition, he said.

About 36,000 hectares (88,958 acres) of coral reef, mangroves and sea-grass could be affected by the oil slick, according to Filipino marine scientists.

Japan has also sent a team of coast guard personnel to help in the cleanup, according to the Philippines' disaster agency, while five U.S. coast guard personnel have arrived to help with the spill response, the U.S. embassy said.

The U.S. National Oceanic and Atmospheric Administration will work closely with the Philippines to conduct rapid environmental assessments of affected areas and assess needs for ecosystem restoration, the embassy said.

The Philippines' environment ministry said it was also in talks with other Southeast Asian countries on further assistance.

Authorities have imposed fishing and swimming bans in affected areas, resulting in disruptions to livelihood of thousands of residents and tourism businesses.