Egyptian jets bombed ISIS targets in Libya on Monday, the day after a video surfaced showing Islamic State members beheading 21 Egyptian Christians, reports Reuters.

Egypt said the early morning airstrike hit militant training sites, camps and arsenals in neighboring Libya.

Libya's air force also participated in the dawn attack on Derna. The coastal city is a base for Islamic State fighters in Libya.

"There are casualties among individuals, ammunition and the (Islamic State) communication centers," Libyan air force commander Saqer al-Joroushi told Egyptian state television.

Al-Joroushi said 40-50 militants were killed, but it is not possible to confirm those numbers.

"More air strikes will be carried out today and tomorrow in coordination with Egypt," Joroushi said.

While it is believed Egypt has supported a Libyan general fighting militants in Tripoli, the mass beheadings have prompted President Abdel Fattah al-Sisi to expand his battle against the Islamic State.