were released. On April 15, four Indonesian sailors were kidnapped when two Indonesian tugboats from Cebu, Henry and Cristi, were attacked by Abu Sayyaf militants. While five of the passengers were safe, one was shot before he was rescued. They were released on May 11. A group of concerned Filipinos in Sabah urged Philippine president-elect Rodrigo Duterte to intervene for the release of four Malaysians held hostage by Abu Sayyaf. The issue strained the relationship between the Philippines and Malaysia. On June 21, seven Indonesian sailors were kidnapped while aboard a tugboat passing through the Sulu Archipelago. On July 9, three Indonesian fishermen were kidnapped near the coast of Lahad Datu, Sabah, Malaysia and released on September 17. On July 18, five Malaysian sailors were abducted near the coast of Lahad Datu. On August 3, an Indonesian sailor was kidnapped in the waters of Malaysia leaving two other crew members unharmed. This incident was reported by victims on August 5. Two of the hostages managed to escape after receiving persistent threats of beheading. On September 10, three Filipino fishermen were kidnapped on the shores of Pom Pom Island. On September 22, another Indonesian hostage was released. On September 27, one Malaysian boat-skipper was kidnapped from his trawler by seven armed militants before the group attacked another Indonesian trawler; however, no kidnappings were committed in the second incident. The hostage was released on October 1, with no ransom demand, along with three Indonesians hostages who were released the same day. On October 21, approximately ten Abu Sayyaf militants attacked a South Korean-bound vessel named MV Dongbang Gian and abducted a South Korean skipper and a Filipino crewman off Bongao, Tawi-Tawi. On November 5, German sailor Sabine Merz was shot dead while her husband Jürgen Kantner was abducted from their yacht off Tanjong Luuk Pisuk in Sabah. On or before February 27, 2017, Kantner was beheaded after a ransom of 30 million pesos ($US600,000) was not paid. On November 11, Vietnamese vessel MV Royale 16 with nineteen sailors on board was attacked by Abu Sayyaf near Basilan, abducting six sailors and injuring one. The remaining thirteen sailors were released. On November 20, two Indonesian fishermen were kidnapped by five gunmen off Lahad Datu. Due to the increase of attacks against foreign vessels by Abu Sayyaf, the governments of Indonesia, Malaysia, and the Philippines agreed to jointly patrol their waters on May 5,