The Philippine Coast Guard said four Chinese vessels were conducting illegal marine scientific research in its waters and threatened to deploy aircraft and boats to repel them.

“PCG has determined that they are conducting illegal marine scientific research without the legal authority or prior consent of the Philippine government, in clear violation of the United Nations Convention on the Law of the Sea,” according to a statement posted on Facebook by Coast Guard spokesman Rear Admiral Jay Tarriela. The Philippines will deploy aircraft and vessels to drive away the Chinese ships, he said.