THE country’s chief diplomat on Monday said China should explain the entry of its warships into Philippine waters after reports that the vessels had turned off their transponders during their so-called innocent passage.

“That’s the other thing China must explain when it claimed that storms buffeted its gray ships off course in circles,” Mr. Locsin yesterday said in a social media post.

“Just the same, is anybody checking what the weather was in place the last batch of warships rightfully exercising ‘innocent passage’ dawdled in our waters?” he added.

This followed reports that Chinese warships have been entering Philippine territory with their automatic identification systems turned off. The Chinese government has said the warships were trying escape bad weather.

“Does innocent passage require helping the coastal state to monitor the innocence of a maritime passage by keeping its automatic identification systems on?” Mr. Locsin said in a separate post. “I know it is aggravating to think the other side might be right but would western navies turn off their systems?”

Mr. Locsin also urged Congress to pass a bill that will establish the Philippines’ archipelagic sea lanes.

“We can start by passing former Senator Antonio Trillanes’ bill defining our archipelago,” the Foreign Affairs chief said. “Oddly it is not easy to do that because it requires the consent of surrounding states, so I am told.”

Mr. Locsin said his department had fired off diplomatic protests over the presence of Chinese vessels within the Philippines’ exclusive economic zone.

Defense Secretary Delfin N. Lorenzana earlier frowned on the unannounced entry of Chinese warships in Philippine waters.

The Armed Forces of the Philippines said at least five Chinese warships had entered Sibutu Strait in Tawi-Tawi in southern Philippines without notifying Philippine authorities.

Presidential spokesman Salvador S. Panelo earlier said the act violated international law.

The Philippines should expect more frequent passage of Chinese warships through its waters as China expands its naval reach, according to Jay L. Batongbacal, director of the University of the Philippines Institute of Maritime Affairs and Law of the Sea. — Charmaine A. Tadalan