Philippine President Rodrigo Duterte may declare nationwide martial law next week if threatened massive protests by communists and other leftists against his rule turn violent or disrupt the country, his defence chief said Friday."He said, if the left will try to have a massive protest, start fires on the streets, they will disrupt the country, then I might (declare martial law)," Defence Secretary Delfin Lorenzana told reporters, recounting a conversation with Duterte this week.