Jakarta – An angry mob on the Indonesian island of Bali has attacked the offices of international conservation group World Wide Fund for Nature (WWF), demanding a recent ban on trading green turtles be lifted.

They were among more than 100 protesters who marched on the WWF office in Bali's capital Denpasar yesterday, the group's program director Tim Jessup said today.

Armed with bamboo sticks and threatening to burn the building, members of the crowd stormed inside and smashed a whiteboard where the group's plans for turtle conservation were written in Indonesian, Jessup said.

As chaos reigned outside, police had to escort the WWF's campaign leader, Ketut Sarjana Putra, into the building to talk with the traders. "They spray-painted graffiti outside saying 'this is the headquarters of friends of the turtles'," Jessup said.

Turtle is a popular food on the tropical tourist island of Bali and it is also used sparingly in ceremonies for the island's Hindu religion. Hunting turtles was banned nationally last year by Jakarta but trade in turtles on Bali continued this year until the provincial government banned their import in July.

"It takes time to disseminate the new regulations to fishermen," said Herranto Effendi, an official from the Natural Resource Conservation unit in Bali's Forestry Department.

But a crackdown is underway. A jail sentence of two months has already been handed down for the capture of two turtles, while a case involving around 100 animals is pending, according to Herranto. He said authorities were also targeting the restaurants in Bali that served turtle meat.

Meanwhile, the office of Bali's governor is negotiating with turtle traders to allow a small quota of turtles to be killed for religious purposes.

WWF estimates that until recently, tens of thousands of turtles a year were being traded in the market. Adult green turtles, worth Rp 300,000 ($A67) could still be bought in the market, the group said.

Intensive harvests using modern fishing techniques could be affecting populations beyond the immediate waters of Bali, Jessup said. "We believe that some of those turtles caught in Indonesian waters spend some of their life in Australian waters," Jessup said. "It gives some indication of the need to manage conservation on a very wide scale."