MANILA, March 9, (Agencies): Philippine President Rodrigo Duterte on Thursday pleaded for help from mayors in Muslim parts of the south to deal with Islamist militants, and threatened to impose martial law there if the problem is not tackled.The largely Roman Catholic Philippines has been struggling to thwart two small but violent Islamic Statelinked groups behind kidnappings, piracy, bombings and the recent beheading of a German captive. “I plead before you because I do not want the trouble in (the southern island of) Mindanao to spin out of control,” Duterte told mayors in a speech in Davao. “Because then, as president, I will be forced, I will be compelled, to exercise the extra-ordinary powers.”He added: “Help me. If not, you know, martial law, then I have to authorise the military just to arrest them, detain you.” The Philippines is fighting Abu Sayyaf militants on two remote islands in the south. The government is seeking the support of separatists who are talking peace with the government to root out groups with extremist agendas.