I will never forgive IS, says Japanese PM

Japanese Prime Minister Shinzo Abe Sunday vowed to "never forgive" the Islamic State (IS) terror group after a video purporting to show the beheading of Japanese journalist Kenji Goto was uploaded online.

"I am infuriated by these inhumane and despicable acts of terrorism, and resolutely condemn these impermissible and outrageous acts. I will never forgive these terrorists. I will work with the international community to hold them responsible for their deplorable acts," Abe said in a statement posted on Japan's foreign ministry website.

He expressed his grief, saying "I am rendered simply speechless".

"When I think about the unbearable pain and sorrow that his family must be feeling, I am rendered simply speechless. As a government, we have pursued every possible means to save their lives. We feel greatest sorrow and profound grief."

Prime Minister Abe said Japan will never give in to terrorism. "We will further expand our humanitarian assistance in the Middle East in areas such as food and medical care. Japan will steadfastly fulfill its responsibility in the international community combatting terrorism," he said.

To allay fears that Japan will be targetted by the Sunni radical group, Abe said his government "will continue to take all possible measures to ensure the safety of Japanese nationals at home and abroad".

He also thanked the world leaders for their support. "I wish to express my heart-felt gratitude to the world leaders, our friends, who have kindly extended their strong solidarity against these acts of terrorism and cooperation toward the release of the hostages."

The IS militants claimed in a video late Saturday to have beheaded freelance journalist and film-maker Kenji Goto, 47, after his compatriot Haruna Yukawa was killed only a few days back. Goto was known to have gone to Syria in October to secure Yukawa's release.

In the one-minute video clip, purportedly posted by the IS, a man believed to be Goto appears kneeling on the ground, wearing an orange jumpsuit, with a masked man, clad in black and wielding a knife standing behind the hostage.

The masked man in the gruesome video said: "...because of Japanese Prime Minister Shinzo Abe's reckless decision to take part in an unwinnable war... (this) knife will not just slaughter Goto, but will also carry on and cause carnage wherever Japanese people are found."

After the video was posted online, Abe told reporters that he was utterly "outraged by the despicable terrorist act", adding that he would never yield to terrorists.