A former head of the Arab League has called for the UN Security Council to approve military action against Islamic State militants.
Amr Moussa - who is also an ex-Egyptian presidential candidate - has spoken after his country carried out bombing raids on targets in Libya.
The bombings came a day after militants murdered 21 Egyptian Coptic Christians.
Mr Moussa says there is a clear threat to the West:
A Libyan air force commander told Egyptian state television that 40-50 militants were killed in bombing raids, while two security officials said civilians, including three children and two women, died.
The strikes came after a video emerged showing handcuffed Coptic hostages dressed in orange jumpsuits being murdered on a beach by militants calling themselves the Tripoli Province of Islamic State.
The Egyptian victims had travelled to Libya for work and were kidnapped in two groups in December and January from the coastal city of Sirte.
In the footage, a camouflaged fighter points north across the Mediterranean and threatens in American-accented English that IS, which already controls around a third of Iraq and Syria, will soon reach Europe.
Saqer al-Joroushi of the Libyan air force said the strikes by war planes loyal to the official government had been coordinated with Egypt and more would follow.
He said Egyptian and Libyan planes had combined to hit targets in the eastern town of Derna. Libyan planes then attacked the central cities of Sirte and Ben Jawad.
Egyptian planes later returned for a second wave of airstrikes on Derna.
A spokesman for Egypt's Armed Forces General Command said the raids were "to avenge the bloodshed and to seek retribution from the killers".
"Let those far and near know that Egyptians have a shield that protects them," the statement added.
'Barbaric and inhumane act'
Egypt's Copts are the largest Christian community in the Middle East and are estimated to account for around 15% of the country's population.
Britain's prime minister David Cameron described the killings as "a simply barbaric and inhumane act", and warned Libya must not become a "safe haven for terrorists".
In the aftermath, Egypt's president, Abdel Fattah al-Sisi, threatened to carry out a "suitable" punishment.
Foreign Minister Sameh Shoukry said "tough intervention" against the militants in Libya is needed or they would threaten world peace.
French President Francois Hollande and Mr al-Sisi have urged the UN Security Council to meet and consider new measures to tackle the militants.
Meanwhile, Libya's internationally recognised prime minister, Abdullah al-Thinni, has called on the West to launch airstrikes on militants in his country.
The country is split between rival governments backed by different militias: Mr al-Thinni's, which is based in Tobruk, and another located in Tripoli.
The Tripoli-based parliament strongly condemned the Egyptian strike on Derna as an "assault against Libyan sovereignty"
