Japanese Prime Minister Fumio Kishida expressed his deepest condolences to President Ferdinand Marcos Jr over the passing of former Foreign Affairs Secretary Albert del Rosario, Ambassador to the Philippines Kazuhiko Koshikawa said in his Twitter account on Thursday.

'' PM Kishida has been a good friend of Secretary Del Rosario since he was Foreign Minister,'' said the ambassador.

Del Rosario, 83, passed away in a plane en route to San Francisco on Tuesday, the Department of Foreign Affairs said.

Del Rosario led the country's filing of a complaint against China over the latter's claim over the South China Sea before the Arbitral Tribunal at The Hague.

The Arbitral Tribunal ruled in 2016 that the Chinese claim has no basis. DMS