CAIRO — The Islamist-backed faction in Libya’s civil conflict said Tuesday that it had carried out its first airstrike, targeting opponents in the town of Zintan in an escalation of the violence tearing the country apart.

The attack occurred two days after the Islamic State, the extremist group also known as ISIS or ISIL, released a video showing fighters for one of its Libyan branches beheading as many as 21 Egyptian Christians. In retaliation, Egypt carried out an airstrike on Monday against a town in eastern Libya that is a hub of Islamist militancy and the home of another Islamic State branch.

The extent of the damage was unclear. But the attack on Tuesday raised the possibility of an air war between the rival Libyan factions and diminished hopes for United Nations-sponsored talks about ending the conflict.

“This may well upend the U.N.’s mediation efforts,” said Wolfram Lacher, a Libya researcher at the German Institute for International and Security Affairs.