CAIRO (AFP) - Army chiefs from Arab League nations on Wednesday began work on building a region-wide military force aimed at combatting extremists including the Islamic State in Iraq and Syria (ISIS).

The regional bloc agreed in March to set up the force, with member states given four months to decide on its composition, precise rules of engagement and required budget.

The meeting to discuss such details was overseen by the Egyptian Armed Forces' Chief of Staff Mahmud Hegazy at the League's Cairo headquarters.

Egyptian President Abdel Fattah al-Sisi has pushed for the creation of the regional force after ISIS executed a group of Egyptian Coptic Christians in Libya in February, prompting retaliatory air strikes by Cairo.

The plan gained further momentum after Saudi Arabia and its Arab allies launched air strikes on Iran-backed Shi'ite Houthi rebels in Yemen.

"The creation of a joint Arab force in no way aims to form a new alliance or army hostile to any country, but a force to fight terrorism and maintain security, peace and stability in the region," Arab League chief Nabil al-Arabi said in a speech Wednesday.

Hegazy said there was a need to "fight terrorism", adding that the force might intervene in internal conflicts.

"We cannot ignore internal conflicts and the growth of terrorist organisations in an Arab country, and it is wrong to think that these conflicts have no direct or indirect repercussions in other Arab countries," he said.

Wednesday's meeting will make proposals to the Arab heads of state that are expected to be ratified within three months.

Egypt, the most populous Arab country, appears set to become the backbone of the force.

Cairo sees it as imperative to intervene in Libya against the local branch of ISIS that is gaining ground in the country.

ISIS has carried out widespread atrocities in the region and won the support of several other extremist organisations.

On Sunday it released a video purportedly showing the execution of about 30 Ethiopian Christians captured in Libya.