The Archbishop of Canterbury has condemned terror attacks in Libya, Denmark and Nigeria in recent days, calling for "deep compassion for the bereaved and killed".
The Most Rev Justin Welby called the beheading of Christian hostages in Libya by Islamic State (IS), shootings in Denmark and a suicide bombing in Nigeria "terrible cruelty".
The killers seem to rejoice in ever more extreme acts carried out to inflict ever greater terror. We must all weep with those affected, and know that in the love of Christ all evil will be overcome.
In Egypt and Libya, the home of Christian faith, of saints and martyrs since the earliest centuries, more suffering has been perpetrated. The Coptic church has responded with courage and as always with faith.
The darkness which Isis seek to spread will be overwhelmed by the faithful lives of Christians shedding the light and peace of Christ. I have been in touch with the Anglican Church in Egypt to express solidarity.
Let us pray for the triumphant peace of Christ to be evident, and for governments affected to be wise and courageous."
Egypt called on the U.S.-led coalition fighting Islamic State in Syria and Iraq to confront militants in Libya, a day after the group released a video showing the beheading of 21 Coptic Christian Egyptians there.
Referring to IS by the Arabic acronym Daesh the Foreign Ministry said in a statement: "Egypt renews its call for the international coalition against the Daesh terrorist organisation...to take the necessary measures to confront the terrorist Daesh organisation and other similar terrorist organisations on Libyan territories".
French President Francois Hollande and Egyptian President Abdel Fattah al-Sisi have called for a UN Security Council meeting to discuss the security situation in Libya after Egypt's military launched air strikes against Islamic State targets there.
The strikes came hours after the apparent beheadings of 21 Egyptian Christians in Libya.
"They underscored the importance of the (U.N.) Security Council meeting and of the international community taking new measures to face up to the danger" of the Islamic State, Hollande's office said after the two leaders' telephone conversation.
A Libyan Air Force commander said 40-50 militants were killed in airstrikes on Islamic State targets in the country, according to Egyptian state television.
Saqer al-Joroushi said: "There are casualties among the individuals, ammunition and the communication centres belonging to them. The number of deaths are not less than 40 or 50 for sure".
French President Francois Hollande has condemned the "savage" killing of 21 Egyptians in Libya by Islamic State and said France and its allies were determined to fight the militants.
Mr Hollande condemned the killings by Daesh, his office said in a statement, using an acronym for Islamic State.
"He expresses his concern about the extension of Daesh operations in Libya and reminds of the determination of France and its allies to fight against this group," his office said.
Egypt's military carried out dawn bombings of Islamic State targets in Libya today, according to reports by state television.
It comes after militants released a video appearing to show the beheading of 21 Egyptian Christians in Libya.
The attack targeted Islamic State camps, training sites and weapons storage areas.
The President of Egypt, Abdel Fattah al-Sisi, has declared seven days of mourning for the 21 Egyptian Christians beheaded in a video released by Islamic State militants.
al-Sisi has also warned Cairo would choose the "necessary means and timing to avenge the criminal killings".
The White House has condemned what it called the "despicable and cowardly murder" of 21 Egyptian citizens in Libya.
The Coptic Christians were kidnapped and killed in a video released by militants associated with the Islamic State terror group.
This wanton killing of innocents is just the most recent of the many vicious acts perpetrated by ISIL-affiliated terrorists against the people of the region, including the murders of dozens of Egyptian soldiers in the Sinai, which only further galvanizes the international community to unite against ISIL.
This heinous act once again underscores the urgent need for a political resolution to the conflict in Libya, the continuation of which only benefits terrorist groups, including ISIL.
Foreign Secretary Philip Hammond has condemned the Islamic State murder of 21 kidnapped Egyptian Christians.
In a statement, he said: "Such barbaric acts strengthen our determination to work with our partners to counter the expanding terrorist threat to Libya and the region.
"Acts of terrorism should not be allowed to undermine Libya's political transition," he added.
"We remain fully supportive of the UN's efforts to build a national unity government for Libya and to bring a political solution to the ongoing security crisis.
"Those who support terrorists can have no part in this process."
Egypt's Preisdent says the country reserves the right to respond in a way it sees fit after Islamic State militants claimed to have beheaded 21 Egyptians in neighbouring Libya.
Speaking on national television, Abdel Fattah al-Sisi warned Cairo would choose the "necessary means and timing to avenge the criminal killings".