CAIRO — The death toll in the attack by gunmen on a bus transporting Christians to a monastery south of Cairo rose to 29, Egyptian authorities said Saturday.

The Egyptian Cabinet said in a news release that 13 victims of Friday’s attack remained hospitalized in Cairo and the southern province of Minya where the attack took place. Authorities had previously said 28 were killed.

There was no immediate claim of responsibility for the attack, the fourth to target Christians since December, but it bore the hallmarks of the Islamic State group. The bloodshed came on the eve of the start of the Muslim holy month of Ramadan.

Hours after Friday’s attack, President Abdel-Fattah el-Sissi announced that Egypt had launched airstrikes against militant training bases in Libya.

Senior Egyptian officials said fighter jets targeted bases in eastern Libya of the Shura Council, an Islamist militia known to be linked to al-Qaida, not the Islamic State grop. There was no immediate word on damage or casualties.

El-Sissi told Pope Towadros II, the pope of the Coptic church in Egypt, in a phone call on Friday that the state would not rest easy until the perpetrators of the attack were punished.

El-Sissi declared a three-month state of emergency following the targeting of two churches north of Cairo on Palm Sunday. In December, a suicide bomber targeted a Cairo church. The three attacks, for which the Islamic State group claimed responsibility, left at least 75 people dead.

Egypt’s government has been struggling for the last three years to deter militants led by an Islamic State group affiliate and centered in the Sinai peninsula.

After a visit to Egypt last month by Pope Francis, IS vowed to escalate attacks against Christians and urged Muslims to steer clear of Christian gatherings and Western embassies.