A British medical student's father is reported to have initially stated that his jihadist son was part of the Islamic State militants seen beheading Syrian soldiers in an online video released over the weekend, only to deny the claims late on Monday, according to conflicting reports.

Ahmed Muthana, from the Welsh city of Cardiff, said his 20-year-old son Nasser Muthana was among a group of 16 jihadists who appeared in ISIS's new 15-minute video, which showed the beheadings of at least 14 men believed to be pilots and officers loyal to Syrian President Bashar al-Assad, according to The Daily Mail.

"I cannot be certain, but it looks like my son," he told UK MailOnline. "He must fear Allah now for killing people. How can he expect to face Allah if he is killing human beings?"

But according to a BBC report on Monday, the father changed his stance after a BBC reporter showed him pictures of the ISIS video.

"It doesn't look like him, much difference. This one's got a big nose, my one has a flat nose," he said, declining to comment on what he thought of his son's alleged actions.

"I have not seen my son since November 2013 but that is not my son," Ahmed said.

Additionally, the British Foreign office also declined to comment on the 20-year-old's suspected involvement. But Western intelligence officials are attempting to identify those seen in the video.

The announcement of U.S. aid worker Peter Kassig's death, which was also featured in the ISIS video, comes after the beheadings of two American and two British men by a masked, black-clad militant brandishing a knife and speaking with an English accent, who has been dubbed "Jihadi John" by British media.

Since most of the ISIS militants were unmasked in Sunday's video, the man who is alleged to be Nasser can be seen standing alongside Jihadi John, Reuters reported.

The 20-year-old jihadist, an aspiring Cardiff medical student, grabbed international headlines in June when he appeared in a propaganda video by the ISIS urging Muslims to join the terrorist organization.

His younger brother, Aseel, had also traveled to Syria after both were radicalized in Cardiff, his father told the BBC News in June. Nasser Muthana's school friend, Reyaad Khan, also appeared in the online footage in June, according to multiple media reports.

ISIS, which has captured large swaths of land in Syria and Iraq, includes thousands of foreign militants and has become a magnet for jihadi volunteers from Europe and North America, according to Western intelligence agencies.

Meanwhile, speculations of a 22-year-old French citizen appearing in the recent beheading video were also making rounds on Monday, with French Interior Minister Bernard Cazeneuve deeming it as a "strong likelihood."