At least 50 people have been killed after militants attacked a mosque in the north of Egypt's Sinai Peninsula, the Sky News Arabia TV channel reported on Friday.
Egypt has launched a prolonged anti-terror crackdown few years ago, trying to unroot extremists based in North Sinai.
"It is a cowardly attack that aims to destabilize the [country's] unity, spread bitterness, and make us doubt our abilities", al-Sisi said while addressing the nation, adding, "however, this attack will do nothing but make us stronger and more persistent to combat terrorism". "This incident is another stark reminder of the need to develop a global strategy to fight this menace of terrorism".
"Will be calling the President of Egypt in a short while to discuss the tragic terrorist attack, with so much loss of life. God bless the people of Egypt", he tweeted.
"The world can not tolerate terrorism, we must defeat them militarily and discredit the extremist ideology that forms the basis of their existence", he added.
Smoke rises after an airstrike in the Sinai city of Rafah as seen from Gaza
UK Prime Minister Theresa May and French President Emmanuel Macron also gave their condolences on Twitter, while NATO Secretary General Jens Stoltenberg said his thoughts were with all those affected.
"Four groups of armed men attacked the worshippers inside the mosque after Friday noon prayers". Condolences with all those in #Egypt affected by this evil and cowardly act.
View of the Rawda mosque after a gun and bombing attack on November 24, 2017. "My honest condolences to all those affected and to the people of Egypt". They also blocked off escape routes from the area by blowing up cars and leaving the burning wrecks blocking the roads, three police officers on the scene said, speaking on condition of anonymity because they were not authorized to talk to the press.
"We stand with Egyptians in their war against terrorism and against anyone who tries to harm the Egyptian national security", Palestinian Authority President Mahmoud Abbas said in a statement.
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