Tokyo (AFP) - Prime Minister Shinzo Abe on Sunday denounced as "heinous and despicable" the apparent beheading of a second Japanese hostage by the Islamic State group, as global leaders denounced the jihadists.IS claimed in a video released online Saturday that it had killed 47-year-old Kenji Goto -- the second beheading of a Japanese hostage in a week -- but made no mention of a captured Jordanian pilot it has threatened to kill.Goto, a respected war correspondent, is seen in an orange outfit -- similar to those worn by Guantanamo Bay inmates -- kneeling next to a standing masked man dressed head-to-toe in black with his face covered.The man, who speaks with a British accent, appears to be the same IS militant who has featured in previous execution videos.He directly addresses Abe, saying the killing was the result of "reckless" decisions by the Japanese government -- a possible reference to aid money that Tokyo gave to help refugees fleeing IS-controlled areas in Syria and Iraq -- and would mark the beginning of a "nightmare for Japan".The brief video, whose content has not been verified, ends with the image of a body and a decapitated head on top of it."After an extensive review, we believe it's highly probable" that the video is authentic, government spokesman Yoshihide Suga told reporters.Japan's premier, who appeared on the verge of tears, pledged not to back down and said his government would increase humanitarian aid to the Middle East."I am extremely angry about these heinous and despicable terrorist acts.