Image copyright Getty Images Image caption More than 1,000 Sika deer live in Nara Park

Nine deer have died in Japan's Nara Park over the last four months after swallowing plastic bags, a wildlife group says.

The Nara Deer Preservation Foundation said they found huge masses of plastic bags and food wrappers in the stomachs of nine of the 14 deer that died between March and June.

One animal was found to have over 4kg (9lbs) of rubbish in their stomach.

Nara, a popular spot for tourists, is home to over 1,200 free-roaming deer.

The Sika deer are classified as a national treasure, and so are protected by law.

Most of them congregate in Nara Park, which is also home to temples and shrines. Visitors are allowed to feed them specially-made sugar-free crackers without plastic packaging.

However, it is thought that some visitors may have fed the deer other snacks.

Rie Maruko from the Nara Deer Preservation Foundation told Kyodo News Agency that tourists often discard food wrappers and plastic bags on the island. The deer then smell the bags, think they are food and then eat them.

On Twitter, the foundation shared a photo of the mass of plastic bags found inside one of the deceased deer.

It is thought that the deer may have died from malnutrition after their stomachs became blocked with plastic.

On Wednesday volunteers took part in a mass clean-up of the park, collecting over 31kg (68lbs) of plastic waste.

Nara prefecture's government is planning to investigate the animals' deaths and set up signs in the park with illustrations to warn tourists about the dangers of feeding the animals food that has not been approved.