The latest issue of the Islamic State (ISIS) online propaganda magazine featured images purporting to show the bomb that was used to destroy a Russian passenger jet in mid-air almost a month ago, and of two more hostages in yellow jumpsuits whom the militants allegedly executed.

A report in the ISIS' Dabiq magazine said the jihadist group has executed Norwegian Ole-Johan Grimsgaard-Ofstad, 48, and Chinese citizen Fan Kinghui, 50, but gave no details about when, where or how they were killed. The group has previously demanded ransom from the respective government of the two captives, according to USA Today.

Dabiq magazine also showed a photo of a Schweppes Pineapple Gold soft drink can and two small devices with wires, apparently referring to them as those used to kill the 224 people aboard the Russian Metrojet bound for St. Petersburg that crashed in Egypt's Sinai about 23 minutes after taking off on Oct. 31, according to the SITE Intelligence Group, a US-based organisation that monitors extremists' activity online.

Dabiq also displayed passports it said came from some of the dead.

"The divided Crusaders of the East and West thought themselves safe in their jets as they cowardly bombarded the Muslims of the Caliphate," Reuters quoted the magazine as saying. "And so revenge was exacted upon those who felt safe in the cockpits."

Norwegian Prime Minister Erna Solberg said there was no reason to doubt the claim, and called it a "barbaric act,'' according to BBC.

Chinese President Xi Jinping also condemned the killing of a Chinese citizen, commenting that "terrorists are the common enemy of humankind,'' Xinhua news agency said.

"Ever since the Chinese citizen was held hostage by the Islamic State group, the Chinese government has been sparing no effort in rescuing him," ministry spokesman Hong Lei said in a statement, according to the AP. "We are still verifying the information."

The militants had announced the two men's capture in a previous issue of Dabiq, BBC said.

The latest report comes as Russia's Federal Security Service announced that "traces of foreign explosives" were found in debris recovered from the crash site.

The ISIS, which has overrun a swath of Syria and Iraq, said it took advantage of a security weakness at Egypt's Sharm el-Sheikh airport to get the bomb on the plane. The militant's affiliate in the area, a group named Sinai Province, has emerged as an effective terror organisation over the past few years, it said.

"FSB and law enforcement agencies of the Russian Federation are taking measures to detect the people involved in the crime," said Alexander Bortnikov, head of Russia's security, according to the TASS news agency.