Updated

The wife of the late Japanese painter Ikuo Hirayama concealed around $3 million worth of her husband's assets to avoid a hefty tax bill, reports said Saturday.

Hirayama, a UNESCO goodwill ambassador who campaigned for the preservation of the world's cultural heritage, died in 2009 leaving assets worth more than one billion yen ($10 million) mostly in the form of artwork, leading newspapers said.

Most of the assets were donated as non-taxable items to an art museum named after him, but his 87-year-old wife failed to report some 200 million yen in cash which was kept at home, the Yomiuri and the Asahi newspapers said, citing unnamed sources.

She also reported the value of copyrights inherited from her husband at around 100 million yen less than the real amount, the reports said.

She was forced to pay 150 million yen in back taxes and penalties, the reports said.

Hirayama was known for his efforts to preserve cultural treasures such as the Angkor Wat temples in Cambodia, China's Mogao Caves and Afghanistan's Bamiyan Buddhist monuments, which were blown up in 2001 by the Taliban.

He was first recognised widely for his 1959 work "Bukkyo Denrai", depicting an ancient Buddhist monk who carried the religion from India to China.

Hirayama created a series of Buddhist-themed paintings of landscapes and ancient ruins on his frequent trips to sites along the ancient Silk Road.