Addis Ababa (AFP) - Ethiopia condemned Sunday the reported killing of Ethiopian Christians captured in Libya, and vowed to continue its fight against Islamist extremists.

"We strongly condemn such atrocities, whether they are Ethiopians are not," Ethiopian Minster of Communications Redwan Hussein told AFP.

Ethiopia's embassy in Egypt was working to verify if those killed were indeed Ethiopians, he added.

The Islamic State jihadist group on Sunday released a video purportedly showing the executions of some 30 Ethiopian Christians captured in Libya.

The 29-minute video purports to show militants holding two groups of captives, described in a text on the screen as "followers of the cross from the enemy Ethiopian Church".

A masked fighter in black brandishing a pistol makes a statement threatening Christians if they do not convert to Islam.

A large number of Ethiopians leave their country -- Africa's second largest in terms of population with more than 90 million people -- seeking work elsewhere.

Many travel to Libya and other north African nations for jobs, as well as to use it as a stepping stone before risking the dangerous sea crossing to Europe.

Ethiopian troops are fighting in neighbouring Somalia as part of an African Union force battling the Al-Qaeda-affiliated Shebab Islamist insurgents.

"There are elements of IS around Ethiopia who are already carrying out operations, even though under a different name," Redwan said, in reference to the Shebab. "We will keep on fighting them."

Almost two-thirds of Ethiopians are Christians, the majority of those Orthodox Copts -- who say they have been in the Horn of Africa nation since the first century AD -- as well as large numbers of protestants.