Nineteen Chinese nationals have been arrested in waters off Sabah with an illegal catch of more than 70 protected turtles, most of them dead, police said on Tuesday.

Except for five turtles left alive, the rest of the 78 Greenback and Hawksbill turtles had been killed and preserved by the Chinese men from southern Hainan province, police said.

"We have detained 19 crew, Chinese nationals from Hainan, China," said assistant marine police superintendent Husaini Zainal Abidin from Kota Kinabalu.

"We also seized about 78 turtles, and out of the 78, five were alive," he told AFP .

Husaini said marine police made the arrest after encountering the poachers in their China-registered wooden trawler on Monday.

"They tried to get away but our boat manged to detain them after we gave them a warning," he said.

Poached for food

Husaini said finding the carcasses of the turtles was "very, very sad".

"They confessed it ... We believe it's for food and maybe for medicine," he said.

"We are handing them to the fisheries department and we are charging them under the Fisheries Act. The offence is they encroached on our national waters and were poaching the turtles, which are protected species," he said.

The captain of the vessel faced a fine of RM1 million and each of the crew RM100,000 or up to five years in jail, he said.

Turtles are hunted in Malaysia for their meat and shell, but many die after getting entangled in fishing nets in open seas.

China is a major importer of turtles from Asia for food and medicinal purposes and aggressive illegal poaching in Southeast Asian countries has seen sea turtle numbers falling.