Sufi Muslims in Egypt say they plan to continue plans for an annual celebration of the birthday of their prophet, Mohammed, even as the country reels from the massacre at a Sinai mosque that killed 305 worshippers and wounded another 128.
No group has claimed responsibility for Friday's attack, widely believed in Egypt to have been launched because Sufis worshipped at the Al-Rawdah Mosque in a village by the same name. Sufis are members of a mystic movement within Islam and are viewed as heretics by Islamic militants.
The Sufis said they will mark Mohammed's birth date next Friday throughout the country and at Cairo's Al-Hussein mosque, one of Islam's most prominent sites in Egypt.
On orders from President Abdel-Fattah el-Sissi, Egypt is observing three days of mourning for the slaughter that unfolded just as an imam was about to deliver his sermon. Shouting Allahu Akbar, or God is great, 25 to 30 militants opened fire and tossed grenades at the estimated 500 people inside the mosque.
In a televised address, the Egyptian leader vowed the use of "brute force" against the attackers, who fled the mosque as they fired shots at ambulance workers arriving on the scene to help the victims of the attack.
"The armed forces and police will forcefully take revenge for our martyred sons and restore security and stability in the short period ahead," Sissi said. He ordered a mausoleum be built in memory of the victims of the attack.
Hours after Sissi spoke, the Egyptian army said air force jets had attacked the "terrorists and discovered several vehicles used in the terrorist attack, killing those inside near the vicinity of the attack."
One survivor of the massacre at the mosque, Ebid Salem Mansour, a 38-year-old worker in a salt factory, told the Associated Press, "Everyone lay down on the floor and kept their heads down. If you raised your head, you get shot." He said, "The shooting was random and hysterical at the beginning and then became more deliberate. Whoever they weren't sure was dead or still breathing was shot dead."
Nabil Sadeq, Egypt's chief prosecutor, said in a statement that some of the attackers were masked and others were bare-faced. One, the statement said, carried a black banner matching those carried by the Islamic State, but the jihadist group has not claimed responsibility for the attack.
An Islamic State affiliate has been carrying out attacks in the Sinai since 2013.
Stephen Zunes, University of San Francisco political professor and chair of Middle East Studies, said the attack marked an escalation in militants' willingness to go after civilians in Egypt.
"This is the largest, by far, terrorist attack in Egypt’s modern history," Zunes told VOA. "Initially they were able to take advantage of the widespread discontent with Sissi’s authoritarian rule, and most of ISIS’s attacks have been against police stations and concentrations of troops, other government facilities."
Saudi Arabia's Crown Prince Muhammad bin Salman said Sunday at the first high-level meeting of a Saudi-led alliance of Muslim nations against terrorism that the attack in Egypt was a "painful event" and a reminder of the dangers of terrorism.
"The biggest threat from terrorism and extremism is not only killing innocent people and spreading hate, but tarnishing the reputation of our religion and distorting our belief," he said.
U.S. President Donald Trump reacted to the violence, calling it a "horrible and cowardly terrorist attack on innocent and defenseless worshippers."
Neighboring Israel sent condolences to Egypt following the attack. Israel and Egypt signed a peace treaty in 1979 and maintain close security cooperation.
Battling Islamic State
Egypt's security forces are battling an Islamic State insurgency, mostly in the northern region of Sinai, where militants have killed hundreds of police officers and soldiers since fighting there intensified in the past three years.
Militants have targeted security forces, but have also struck beyond the Sinai by hitting Christian churches and civilians in other parts of Egypt.
Egyptian media reported that Sissi met with top security officials, including the defense and interior ministers, immediately after the attack as security was stepped up around government buildings.