Cairo - Egypt has arrested four people suspected of involvement in a Cairo church bombing last month that killed 27 people, the interior ministry said on Wednesday.
Those detained include one of the two main suspected plotters of the attack, Karam Ahmed Abdel-Aal Ibrahim, and three others who were planning other attacks, the ministry said in a statement.
The death toll from the December 11 suicide bombing during Sunday mass at the Saint Peter and Saint Paul church rose to 27 on Wednesday after a 63-year-old woman died of her injuries, the health ministry said.
Eleven people remain in hospital, it said.
The interior ministry said authorities are still searching for Mohab Mostafa el-Sayed Qassem, also known as "The Doctor", previously identified by the interior ministry as the group's leader.
The ministry said investigations revealed one of the three men arrested has links to the Muslim Brotherhood and had attended rallies of the Islamist movement while armed.
The interior ministry has said Qassem received financial and logistical support and instructions to carry out the attacks by Brotherhood leaders residing in Qatar.
The Islamic State group claimed responsibility for the bombing, identifying the suicide bomber by the pseudonym Abu Abdallah al-Masri.
President Abdel Fattah al-Sisi had named the suicide bomber as Mahmoud Shafik Mohamed Mostafa, 22.
The Muslim Brotherhood has denied any involvement.
Egyptian authorities are battling an Islamist insurgency, mostly in the province of North Sinai. Some attacks have targeted security forces and officials in Cairo.
The attacks have worsened since the July 2013 ouster of Brotherhood president Mohammed Morsi, which was led by then army chief Sisi.
Last month's blast was the worst attack on the Coptic Christian community since a 2011 suicide bombing killed more than 20 worshippers outside a church in the coastal city of Alexandria.