Fourteen letters discovered at a temple in Nagoya last year were written by Eisai, founder of a major Japanese Zen Buddhist sect, a group of researchers said Wednesday.

The letters, found at Osu Kannon Temple in Nagoya, were written by Eisai (1141-1215), a Zen monk who established the Rinzai sect of Zen Buddhism, according to a group of researchers including Nobumichi Inaba, a Nagoya University professor of Japanese history.

Rinzai is one of Japan's two major Zen Buddhist sects and takes its name from the Chinese Zen master Linji Yixuan.

Inaba said that until now, only three handwritten documents attributed to Eisai, also known as Yosai, were thought to exist. Two of them are designated as important cultural assets.

"The (latest) finds should add to our knowledge of Eisai," Inaba said, adding that they shed fresh light on the relationships and disputes among monks at the time.

The letters, discovered in July, are believed to have been written toward the end of the reconstruction of Todaiji Temple, in Nara Prefecture. Most deal with the difficulties of obtaining building materials and the costs of reconstruction.

All written in Eisai's distinctive style, nine of the letters bear his signature and five have marks that are the equivalent of a signature, Inaba said.

The professor added there are a further two documents that may also be credited to Eisai.

Todaiji is a major temple complex established during the reign of Emperor Shomu (701-756) and remains a pre-eminent example of Buddhist architecture. Its centerpiece is the colossal bronze statue popularly known as the Great Buddha of Nara.

After suffering considerable damage, Todaiji was rebuilt under the sponsorship of the Tokugawa Shogunate in 1692. Although the hall housing the Buddha statue lacks the refinement of the original, it remains the largest wooden structure in the world.