Twelve Chinese fishermen whose ship grounded in a protected marine sanctuary in the Philippines could face long jail terms after being charged with poaching and bribery, a prosecutor said Thursday.

The fishermen have been in detention since sanctuary rangers found their vessel on Tuesday jammed onto the UN World Heritage-listed Tubbataha Reef, roughly 1,600 kilometres (1,000 miles) from China's nearest major landmass.

"We will seek to quickly prosecute and resolve this case," Alen Ross Rodriguez, chief prosecutor in the island province of Palawan, which has jurisdiction over Tubbataha, told AFP.

"No one can just enter our waters and willfully destroy our marine life."

Rodriguez said the 12 had been charged with poaching for violating a law that bans fishing in Tubbataha, an isolated reef in the Sulu Sea famed for its spectacular and diverse marine life.

They were also charged with "attempted corruption of public officials" because they tried to bribe the rangers, offering them $2,400 to be released, Rodriguez said.

Both of those charges carry maximum jail sentences of 12 years.

However, Grizelda Mayo-Anda, head of the Environmental Legal Assistance Center in Palawan, said Chinese fishermen caught poaching in Philippine waters were typically deported quickly in an effort to appease China.

"The government has always treated them (fishermen) with kid gloves for political considerations so as not to cause any adverse reaction from China," Mayo-Anda told AFP.

She said more than 600 Chinese fishermen had been caught poaching over the past decade but in nearly every case they spent just a few weeks or months in jail before being deported.

In Beijing, Chinese foreign ministry spokesman Hong Lei said the Philippine government had been asked to "ensure the legitimate rights, benefits and safety of the Chinese fishermen".

The current case comes amid deep tensions between the Philippines and China over competing territorial claims to the neighbouring South China Sea.

The stranded 48-metre (157-foot) boat remained stuck on the reef on Thursday, and was not expected to be removed before the weekend, according to the coast guard.

It was unclear how much damage the boat had caused to the reef.

The incident came after a US Navy minesweeper also got stuck on the reef in January, causing significant damage, and had to be dismantled for removal.