Egypt's president al-Sisi calls for international intervention against Isis in Libya

President al-Sisi is lobbying Europe and the United States for a coordinated international response

President Abdel Fattah al-Sisi makes a statement after Isis released a video purporting to show the beheading of 21 Coptic Christian hostages (AP)

Egypt has called on the US and Europe to join an international military intervention following airstrikes against Isis targets in Libya.

The strikes by Egypt were provoked by a gruesome video posted by the militant group, purporting to show the beheadings of 21 Egyptian Coptic Christian hostages.

The mass murder realised long-held fears of militants reaching the Mediterranean coast.

Islamic State group weapons caches and training camps were targeted "to avenge the bloodshed and to seek retribution from the killers," a military statement said.

"Let those far and near know that Egyptians have a shield to protect and safeguard the security of the country and a sword that cuts off terrorism."

Men mourn over Egyptian Coptic Christians who were killed by Isis militants

Relatives of Egyptian Coptic Christians murdered by Isis militants in Libya react after hearing the news

A Coptic clergyman shows a picture depicting one of the Coptic Christians murdered by Isis militants

Egyptian President Abdel Fattah al-Sisi vowed to avenge the beheading, saying the country reserved the right to respond in a way it sees fit.

He is lobbying Europe and the United States for a coordinated international response.

"What is happening in Libya is a threat to international peace and security," he said.

Al-Sisi spoke with French president Francois Hollande and Italy's prime minister Matteo Renzi, and sent his foreign minister, Sameh Shukri, to New York to consult at the United Nations ahead of a terrorism conference opening on 18 February in Washington.

According to Reuters, al-Sisi told French radio: "There is no other choice, taking into account the agreement of the Libyan people and government and that they call on us to act."

Commenting on the latest Isis video in the UK, foreign secretary Philip Hammond said: “Such barbaric acts strengthen our determination to work with our partners to counter the expanding terrorist threat to Libya and the region.”

France has signalled a readiness for some kind of international action in Libya, and announced a deal on 16 February to sell 24 fighter jets to Egypt.

French President Francois Hollande's office said that he and al-Sisi both "stressed the importance that the Security Council meets and that the international community takes new measures to confront this danger".

A NATO official who spoke on condition of anonymity in keeping with NATO practice said "there is no discussion within NATO on taking military action in Libya."

However, Allies consult regularly on security developments in North Africa and the Middle East and we follow events in the region closely," the official said. "We also stand ready to support Libya with advice on defense and security institutions-building."

Libya is where Isis has built up its strongest presence outside Syria and Iraq. Libyan extremists loyal to the terrorist organisation and some 400 fighters from Yemen and Tunisia have seized control of Darna and the central city of Sirte and built up a powerful presence in the capital, Tripoli, as well as the second-largest city, Benghazi.

Additional reporting by AP