A Philippine court on Monday found nine Chinese fishermen guilty of poaching and environmental crimes for fishing in disputed waters, in a case that has strained relations with China.

The nine, arrested in May, were fined $100,000 each for poaching with an additional 120,000 pesos ($2,730) fine for catching an endangered species, prosecutor Allen Ross Rodriguez said in the town of Puerto Princesa on Palawan island.

Filipino police said they found hundreds of sea turtles -- a protected species -- on board the fishermen's 15-tonne vessel when they arrested the group at Half Moon Shoal.

The shoal is 111 kilometres (60 nautical miles) west of Palawan, the most westerly island in the Philippines. It is located on the eastern edge of the Spratlys island chain.

China claims nearly all of the South China Sea, including Half Moon Shoal and other areas near Palawan that are also claimed by the Philippines.

Philippine Foreign Affairs Spokesman Charles Jose said the court's decision should not further complicate ties with China.

"This is a purely law enforcement matter," Jose told AFP.

A spokeswoman for the Chinese Embassy in Manila could not be reached for comment.

China previously demanded that the Philippines release the fishermen immediately, saying it has "undisputable sovereignty" over the shoal.

It also refused to cooperate in the legal proceedings and failed to provide a defence lawyer or translator for the nine fishermen -- a move which prosecutors said delayed the proceedings.

The Philippine Department of Foreign Affairs provided a translator for Monday's proceedings.

The arrest of the fishermen further worsened relations already soured by the two countries' territorial dispute.

China's claim covers vast fishing areas and shipping lanes which potentially hold valuable mineral resources. It also conflicts with the claims of Brunei, Malaysia, Taiwan and Vietnam.

The Philippines in March filed a formal plea to the United Nations challenging China's claims but Beijing has rejected UN arbitration.

Originally, 11 Chinese were found on the boat but two were found to be minors and were repatriated without charge.

The court also ordered the confiscation of the fishermen's gear and their vessel, which it turned over to the Palawan government.

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