Two Russian mercenaries reportedly captured by ISIS jihadists are feared to have been executed because they refused to read out a statement saying they rejected their Christian faith and had become Muslim.

Roman Zabolotny, 39, and Grigory Tsurkanu, 38, held in Syria, also refused to say on camera that they had joined the terrorist group.

The men are believed to have been fighting for a private Russian mercenary force comprising ex-servicemen which saw action in Crimea and eastern Ukraine before Syria.

They were held by jihadists around the eastern city of Deir Ezzor, the last ISIS stronghold in the country.

They appeared in a video released earlier this week by ISIS news agency Amak which claimed inaccurately that the men were serving Russian soldiers.

Senior Russian MP Viktor Vodolatsky said: 'It is very sad but 99 per cent Roman Zabolotny is not alive, nor is the second prisoner.

'Before filming that video they were given a statement which they had to read.

'In this text they would reject their Orthodox religion, reject their motherland, become Muslim and join ISIS.

'They stayed loyal to the Orthodox faith and their Motherland until the very end, and this is what they were killed by those gangsters for.'

There has been no official confirmation from the Russian authorities about their fate, but Vladimir Putin's government is coy speaking about such mercenary forces in Syria and other hot spots, even though experts say they work closely with the armed forces.

Two suspected Russian mercenaries named in a video as Grigory Mikhailovich Surkanov (left) and Roman Vasilievich Zabolotny (right), are feared dead

One of the men is named in the video as Grigory Mikhailovich Surkanov (pictured). However, he has since been named as Grigory Tsurkanu

A local MP in Rostov-on-Don, Zabolotny's home city, also confirmed the pair had been 'executed', saying it happened the day after the video was made.

'Unfortunately, this is true,' said Anatoly Kotlyarov. 'Information was received that they were executed in a town square.'

His source is 'trustworthy' and 'the person who told me has never been mistaken in four years of our cooperation, especially when informing about the dead', he told Komsomolskaya Pravda newspaper.

When asked if there had been secret negotiations between Russian forces and ISIS over the captives, he said this was 'secret information' which he could not divulge.

An anonymous friend of father-of-two Zabolotny's was quoted saying: 'Last time I saw him he was about to go there.

'And when this video came out that he was captured, I used my own channels to clarify his fate.

'He is dead. Those bastards executed him.'

Zabolotny was reported to have been a devout Orthodox believer and went to Syria in order to protect Christians from terrorists.

A Russian group had offered to pay $1 million to ISIS for each of the men if they were freed.

A Zabolotny family member said they had not been informed he was dead.

'Negotiations are going on, there is no information about his death,' said the relative.

His father Vasily said: 'I am worried about my son, I am hardly coping. I am on the edge, sorry, I don't want to speak more.'

The pair were held by the jihadists around Deir Ezzor, the last ISIS stronghold in the country. One of the men is named in the video as Roman Vasilievich Zabolotny (left)

A day ago it was reported that the parents of Tsurkanu had been told by the FSB secret service 'not to make any noise' in the media amid hopes he would be released soon.

Tsurkanu was a former Russian paratrooper in the intelligence section of the country's air assault forces.

The men were believed to be fighting for a group called Wagner private army.

Ruslan Leviev, founder of Conflict Intelligence independent investigation group, said the pair were mercenaries.

They are believed to be mercenaries belonging to the so-called Wagner private army, allegedly deployed by Moscow in hot spots to lower casualty numbers among regular forces. One of the men, named as Grigory Tsurkanu, is pictured centre

'Our experience of watching this conflict tells us that Wagner private army mercenaries are the first to fight,' he said.

'We think it is a strategy of the Defence Ministry of Russia: sending mercenaries to the hottest places, we avoid losses among official soldiers and keep the image of a successful combat operation.'

Putin's spokesman Dmitry Peskov sidestepped a question about the fate of the men.

'I repeat once again that, of course, the possible circumstances of their captivity and confirmation of their identity are things that are being dealt with by our relevant agencies,' he said.

ISIS news agency Amaq claimed the men were seized near the eastern city of Deir Ezzor.

They can be seen wounded and handcuffed in a video, explaining where they are from in Russia and where they were captured.

In the video, the bearded man can be heard saying: 'I am Zabolotny, Roman Vasilievich, born in 1979, in Rostov region, Aksaisky district, Passvet village.

'During counter attack of ISIS in the area of Cholya settlement I was taken prisoner of war.

'Surkanov, Grigory Mikhailovich was captured together with me, born in 1978, in Domodedovo district.'