MANILA - President Rodrigo Duterte may be impeached if he allowed China to explore an undersea plateau off the Philippines' Pacific coast, an international law professor said Wednesday.

Duterte said Thursday he was "advised way ahead" before Chinese research vessels sailed over Benham Rise. Defense Secretary Delfin Lorenzana earlier expressed concern over the ships' presence.

"Under our Constitution, iyung ganyang activities, dapat under the full control of the state -- kahit exploration pa lang," said Jay Batongbacal, director of the University of the Philippines Institute for Maritime Affairs and Law of the Sea.

(Under our Constitution, such activities should be under the full control of the state -- even mere explorations.)

"Dapat nga nating malaman natin ano ba talagang nangyari dito dahil pwede ngang masabi na baka mamaya, may grounds for impeachment dito kasi culpable violation of the Constitution iyan 'pag ganyan."

(We need to know what really happened here because this may be grounds for impeachment as it could be a culpable violation of the Constitution.)

Batongbacal said he was surprised that Lorenzana appeared unaware of the presence of the Chinese ships.

Lorenzana had said Chinese ships had no business in those waters and that Beijing’s defense of the act as an “innocent passage” contradicted what he saw.

The Department of Foreign Affairs has asked the Chinese Embassy in Manila to explain the incident.

Benham Rise is the latest addition to Philippine territory. It was awarded to the country by the United Nations in 2012 after Manila successfully proved that it is part of Isabela province's extended continental shelf.

Though largely still unexplored, Benham Rise is believed to be rich in oil and natural gas deposits, apart from the marine life that may be exploited from there. -- with a report from Reuters

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