Christians living under the yoke of Islamist extremism in Libya face even greater danger following reports that the Islamic State (ISIS) and al-Qaeda have formed an unholy alliance in the southern part of the country.

"[ISIS] and al-Qaeda have never attacked each other here and now we have evidence that they are actively cooperating," Libyan Defence Minister Mahdi Barghathi told the Daily Telegraph.

"Al-Qaeda is providing logistics and support to help [ISIS] re-group and launch attacks," Barghathi added.

The Libyan defence chief further revealed that Mokhtar Belmokhtar, the former military commander of al-Qaeda in the Maghreb, is leading ISIS fighters who survived the attacks of Libyan forces on the ISIS bastion in Sirte last year.

Belmokhtar was previously thought to have been killed in an airstrike last year. However, his body was not recovered. The al-Qaeda leader is known to have led an attack on a gas plant in Algeria in 2013 in which 37 Western hostages were killed.

The alliance between the two terrorist groups could signal an even more worrisome persecution of Christians still holding out in Libya.

Last January, dozens of Egyptian Christian workers were reportedly trapped in Libya with all roads leading to Egypt blocked by ISIS, which has been waging a campaign of genocide on Christians.

The information came from the persecution watchdog group International Christian Concern (ICC), saying that the more than 30 stranded Coptic Christian workers had traveled to Libya for work to support their families in Egypt.

Egyptian authorities were urged "to intervene and find safe ways to return these men to their homes."

There has been no word yet on whether the stranded Christian workers were able to return home.

Based on their previous pronouncements, ISIS intends to wipe out or drive away all Christians from territories it controls. The terrorist group showed it means what it says when it beheaded 21 Coptic Christians kidnapped in Libya in February 2015. The ISIS even released a video of their gruesome act in what is now considered as one of the biggest mass executions of Christians filmed on camera.

Coptic Orthodox Patriarch Tawadros II officially named the 21 Copts as martyrs of the Church last year.

"These men paid the ultimate price, but gave us a cause to advocate for all those persecuted; they also showed us that there was a level of evil that we must all stand in solidarity against, and a level of courage, faithfulness and defiance that we must all aspire to," said Bishop Amba Angaelos, general bishop of the Coptic Orthodox Church, during the one year anniversary of the massacre last month.