David Cameron has warned Libya must not become a “safe haven for terrorists” after militants loyal to “Islamic State” beheaded 21 hostages.
The Prime Minister condemned the “barbaric” killings of the captives, who were all Coptic Christians from Egypt.
His comments came as security sources said Egypt has launched a second wave of air strikes on positions held by IS –also known as Isil or Isis.
Mr Cameron said: “I am appalled by the murder of Christians in Libya, a simply barbaric and inhumane act. My thoughts are with the families of those killed and the UK stands united with the Egyptian people during this period of mourning.
“Our efforts to defeat the monstrosity of Islamist extremism must not waver.
“The UK remains steadfast in its efforts to defeat Isil and in its work to bring about a political transition in Libya through the UN. We are clear that Libya must not become a safe haven for terrorists.”
Egypt yesterday carried out two waves of air raids on IS targets in the eastern city of Darnah.
It came after a video emerged showing the 21 hostages, who were captured in December and January from the eastern coastal town of Sirte, being forced to the ground before they are beheaded.
The developments have raised fears that IS could establish a firm presence in a country less than 500 miles (800km) from the southern tip of Italy. In the video, a militant suggests that the group now plans to “conquer Rome”.
A Downing Street spokeswoman said the UK was “discussing with Egypt at the moment exactly what action they are taking”.
Asked whether Britain could offer Cairo military support, she said: “Our focus is on the political solution and there are no discussions beyond that at the moment in Government.”
The spokeswoman said IS’s murder of Egyptian nationals “underlines in Libya the importance of finding a political solution”.
Mr Cameron discussed action against Islamist extremists with the Sultan of Brunei during talks at his country residence Chequers. “It is absolutely clear that what we need to be doing around the world is working with other countries to tackle this growing threat from Islamist extremists and their poisonous ideology wherever we find it,” said the spokeswoman.
Asked whether the weekend’s events made Mr Cameron regret his decision to commit UK military forces in Libya in 2011, the Number 10 spokeswoman said: “This was a country where people were being oppressed by a dictator, where they were not able to pursue their aspirations and have their voice heard for a democratic and peaceful Libya.
“The actions we took there and the decision to intervene was an international one.”
Libya is engulfed by political uncertainty and violent power struggles, with the unrest seen as the worst since the overthrow of Muammar Gaddafi in 2011.
Sir Richard Dalton, a former British ambassador to the country, said IS has established a presence in the country following the “disappearance of legitimate authority”.
However, he stressed the scale of IS’s influence appears to be “limited” and played down the possibility of the militant group building a power base similar to those it established in Syria and Iraq.