The militant Islamic State group, which holds territory in Iraq and Syria, issued a video online on Tuesday purporting to show two Japanese captives and demanding $200 million from the Japanese government to save their lives.

A black-clad figure with a knife, standing in a desert area along with two kneeling men wearing orange clothing, said the Japanese public had 72 hours to pressure their government to stop its "foolish" support for the U.S.-led coalition waging a military campaign against Islamic State.

The militant, who spoke in English, demanded "200 million" without specifying a currency, but an Arabic subtitle identified it as U.S. dollars.

The video identified the men as Haruna Yukawa and Kenji Goto.

The video was not dated, but on a visit to Cairo on Jan. 17, Japanese Prime Minister Shinzo Abe pledged around $200 million in non-military assistance for countries battling Islamic State.

Abe was in Jerusalem on Tuesday as part of a regional tour.

In Tokyo, Japan's foreign ministry said it was checking the video to see whether the footage was genuine and said that, if it was, "such a threat by taking hostages is unacceptable and we are extremely resentful."

Goto is a freelance reporter who was based in Tokyo. He has written books on AIDS and children in war zones from Afghanistan to Africa and reported for news broadcasters in Japan.

Goto met Yukawa last year and helped him travel to Iraq in June, he told Reuters in August.

Yukawa's father, Shoichi Yukawa, declined to comment, saying he was overwhelmed by the news reports.

The video resembled others distributed by Islamic State outlets in which captives were threatened or killed.

The militant, who spoke with a British accent, appeared to have the same voice as a jihadist shown threatening captives in previous Islamic State videos.