Islamic State said in the latest edition of its English language magazine on Wednesday that it had killed a Chinese and a Norwegian captive, showing what appeared to be pictures of the dead men under a banner reading "Executed".
The Norwegian Foreign Ministry declined to comment.
In September, Norwegian Prime Minister Erna Solberg said a Norwegian man had been held hostage in Syria since January and was believed to be in the hands of Islamic State.
She said Norway did not intend to pay a ransom for his release. Solberg said the man, named by the foreign ministry as Ole Johan Grimsgaard-Ofstad, was in his 40s and had been held by several groups since he was first captured.
China's Foreign Ministry also said in September that one of its citizens appeared to be in Islamic State captivity.
In the previous issue of the magazine, Dabiq, Islamic State showed pictures of two men who it said were Norwegian and Chinese, wearing yellow suits and with shaved heads.
It said their governments had "abandoned" them, but that they were "for sale" and ransom payments could secure their release.
It identified the Chinese man as Fan Jinghui and said he was a 50-year-old freelance consultant from Beijing. It identified Grimsgaard-Ofstad as a candidate for a masters degree in political science born in 1967.
In its latest issue, it did not give any details about how, when or where they were killed.
The magazine also carried a photo of what it said was the improvised bomb that brought down a Russian airliner over Egypt's Sinai Peninsula last month, killing all 224 people on board.