Egypt's military has carried out dawn bombings of Islamic State targets in Libya, according to reports by state television.
Seven days of mourning were declared in Egypt after Islamic State militants released a video claiming to show the murder of 21 Egyptian Christians kidnapped in Libya.
The video has been condemned by governments around the world, while the Egyptian leadership vowed to respond to the "criminal killings".
David Cameron has spoken to Egyptian president Abdel Fattah el-Sisi to offer his condolences over the murder of the Egyptian Christians and to discuss how Britain and Egypt could work together to fight terrorism.
Mr el-Sisi and the Prime Minister agreed that a political solution was the best way to solve the Libyan crisis.
"The Prime Minister recognised that Egypt, as one of Libya's neighbours, had a particular interest in protecting itself from violent extremism on its borders and that both countries shared the same objective: a safe and secure Libya," a Downing Street spokeswoman said.
The Democratic presidential candidate may also have shown his cards on his choice of running mate.
The US president also shared a post on Twitter accusing Dr Anthony Fauci of misleading the public over hydroxychloroquine.
Fears over an impending second wave of coronavirus dominates Wednesday’s front pages.