Egyptian President Abdel Fattah al-Sisi said on Monday a suicide bomber carried out the attack that killed 25 people at Cairo's Coptic cathedral, the deadliest on the Christian minority in years.
Speaking at a state funeral for the victims, Sisi said four people had been detained, including a woman, and security forces were seeking two more people believed to be involved. The bomber was a man wearing a suicide vest, he added
"The attack brought us great pain but we will never be torn apart," he said. "We will only be much stronger. We will hold steadfast and, God willing, we will succeed."
At least 25 people were killed and 49 wounded when a bomb exploded in a chapel adjoining St Mark's Cathedral, Cairo's largest church and seat of the Coptic papacy, where security is normally tight. (Map: http://tmsnrt.rs/2hEe6V1)
Security sources said a bomb containing at least 12 kg (26 pounds) of TNT exploded on a side of the church normally used by women.
Sisi did not name the organization the attackers were believed to belong to. No group has claimed responsibility, but exiled Muslim Brotherhood officials and local militant groups have joined the international community in condemnation.
Only Islamic State supporters celebrated on social media. The group has also claimed attacks in Cairo and urged its supporters to launch attacks around the world as it goes on the defensive in its Iraqi and Syrian strongholds.
The Interior Ministry released a picture of the bomber it identified as Mahmoud Shafik Mohamed Mostafa, 22, whose nom de guerre was Abu Dajjana al-Kanani. It also released an image of what it said was the battered head of the dead bomber, who hailed from the town of Fayyoum south of Cairo.
State news agency MENA reported that three of those arrested are also from Fayyoum while a fourth is from the Cairo suburb of Matariya. Both are areas typically associated with strong support for the Muslim Brotherhood.
Sisi and Coptic Pope Tawadros II led the funeral procession and the coffins were draped in the national flag.
Earlier, mourners had packed Cairo's Virgin Mary and St Athanasius Church where Tawadros prayed over the wooden coffins. On the walls hung banners with the names of the dead, many of them women.
Tawadros sought to heal any sectarian friction caused by the attack, saying it "is not just a disaster for the Church but a disaster for the whole nation." He also condemned attacks against the security forces.
"Those who commit acts such as this do not belong to Egypt at all, even if they are on its land," he said.
At the chapel where the bombing took place, the floor was covered in debris from shattered windows, wooden pews blasted apart and pillars blackened. Here and there lay abandoned shoes and patches of blood.
At the burial, families arrayed in black queued as a priest called out the names of their deceased relatives before they were interred. A church chorus sung hymns over the cries of those grieving.
Ayman Nosyeh described the shock of seeing his cousin's remains. "Only her mouth was left from her face, her head was empty, like an empty watermelon. I'm the one who put her in the bag. It was a very difficult scene," he said.
Though Christians traditionally support the government, the attack provoked anger among survivors and families of the dead, who said police had failed to protect them.
Five survivors at Dar al-Shefa hospital said police did not conduct the usual checks as the cathedral was particularly busy for Sunday's mass.
Crowds outside the cathedral on Sunday demanded revenge. Some chanted "the people demand the fall of the regime", the rallying cry of the 2011 revolt that ended Hosni Mubarak's 30-year rule.
"There were police cars stationed in front of the church gates ... they were too busy eating breakfast and drinking tea and soda. They weren't doing their job," said Hani Gaballah, 43, a retired military officer.
Sisi dismissed accusations of a security failure and called for tighter anti-terrorism laws to help crush militants. "We will not let this go even after we have arrested them," he said.
Parliament speaker Ali Abdelaal said the constitution would be amended if needed to create tougher laws on terrorism.
Orthodox Copts, who comprise about 10 percent of Egypt's 90 million people, are the Middle East's largest Christian community. They face regular attack by Muslim neighbors, who burn their homes and churches in poor rural areas, usually in anger over an inter-faith romance or church construction.
The last major attack on a church took place as worshippers left a New Year's service in Alexandria weeks before the start of the 2011 uprising. At least 21 people were killed but no one has been punished.
Middle Eastern Christians have felt increasingly insecure since Islamic State spread through Iraq and Syria in 2014, systematically targeting religious minorities.
REUTERS