A bombing at Egypt's main Coptic Christian cathedral killed 25 people and wounded another 35 on Sunday, according to Egyptian state television, making it one of the deadliest attacks carried out against the religious minority in recent memory.
The attack came two days after a bomb elsewhere in Cairo killed six policemen, an assault claimed by a shadowy group that authorities say is linked to the outlawed Muslim Brotherhood. Islamic militants have targeted Christians in the past, including a New Year's Day bombing in Alexandria in 2011 that killed at least 21 people.
Egypt's official MENA news agency said an assailant lobbed a bomb into a chapel close to the outer wall of St Mark's Cathedral, seat of Egypt's Orthodox Christian church and home to the office of its spiritual leader, Pope Tawadros II.
However, witnesses said the explosion may have been caused by an explosive device planted inside the chapel. Conflicting accounts are common in the immediate aftermath of attacks.
An Associated Press reporter who arrived at the scene shortly after the blast saw blood-stained pews and shards of glass scattered across the chapel's floor. Men and women wailed and cried outside the chapel.
"I found bodies, many of them women, lying on the pews. It was a horrible scene," said cathedral worker Attiya Mahrous, who rushed to the chapel after he heard the blast. His clothes and hands were stained with blood and his hair matted with dust.
There was no immediate claim of responsibility for Sunday's attack.
Egypt has seen a wave of attacks by Islamic militants since the military overthrew President Mohammed Morsi, a freely elected leader who hailed from the Brotherhood, in 2013. Many of Morsi's supporters blamed the overthrow on Christians, and several churches and other Christian-owned properties were ransacked in the aftermath.
The authorities have waged a sweeping crackdown in recent years, jailing thousands of mostly Islamist dissidents and killing hundreds in clashes sparked by demonstrations.