Reports from Egypt say the country's air force has launched air strikes against "terrorist camps" in neighboring Libya in retaliation for a deadly attack on Coptic Christians.
State television reported on May 26 that a total of six militant training camps were hit in the eastern Libyan city of Derna.
The reports came minutes after President Abdel Fattah al-Sisi announced in a televised address that he would "not hesitate to strike terrorist camps anywhere, either inside [the country] or outside it."
Sisi said that countries which support terrorism should be punished, and appealed to U.S. President Donald Trump to take the lead in the fight against global terrorism.
"I direct my appeal to President Trump: I trust you, your word and your ability to make fighting global terror your primary task," he said.
Earlier on May 26, at least 28 people were killed and 25 injured in an attack on a bus carrying Coptic Christians, according to Egyptian officials.
They said the attack took place as the Christians were traveling to a monastery about 200 kilometers south of Cairo.
No group immediately claimed responsibility for the attack, but the extremist group Islamic State (IS) has targeted Coptic Christians several times in recent months.
IS militants have threatened to carry out more attacks on Coptic Christians, who make up about 10 percent of Egypt's population of 92 million.
In April, two suicide bombings at churches in the northern cities of Alexandria and Tanta left 46 people dead.
In a statement, Trump said the latest attack should bring nations together to crush "evil organizations of terror."
"The bloodletting of Christians must end, and all who aid their killers must be punished," the U.S. president said. "Terrorists are engaged in a war against civilization, and it is up to all who value life to confront and defeat this evil."
Pope Francis denounced the attack as "barbaric" and urged the country to join in reconciliation, the Vatican said.