Eleven people were killed in an explosion outside Saint Mark's Cathedral in the Mediterranean coastal city of Alexandria, which was reportedly carried out by a suicide bomber. Head of Egypt’s Coptic Church Pope Tawadros II had been attending mass inside, though he was left unharmed, according to the Egyptian state media.
An earlier blast at the Saint George Church in the city of Tanta, located between Alexandria and Cairo, left 25 dead.
The so-called Islamic State reportedly claimed responsibility for both attacks, via its Amaq press agency.
Palestinian President Mahmoud Abbas’s adviser for religious affairs Mahmoud al-Habbash denounced the attacks, which he described as a "criminal act incompatible with the bases of our true religion (Islam)."
Al-Habbash said the attacks sought to stoke unrest and sectarianism between Muslims and Christians in Arab communities, which he said have coexisted in brotherhood throughout the ages.
The Palestinian official rejected terrorism of all types, whether practices by individuals or by groups. "What happened today was a cowardly act, which we denounce in the strongest possible terms."
Al-Habbash affirmed that Palestinian leadership and the Palestinian people would continue to support Egypt in its efforts to counter acts of terrorism that plague the region.
Palestinian government spokesman Yousif al-Mahmoud later released a statement, which described the attacks as "brutal act on a place of worship.”
The Hamas movement also condemned the bombings, described the attacks as "a crime." Spokesman Fawzi Barhum said that "Hamas wishes safety, security, stability, and prosperity for Egypt and its people."
The attacks came on Palm Sunday, one of the holiest days of the Christian calendar, marking the entrance of Jesus to the city of Jerusalem. The incidents also came just weeks before Pope Francis is due to visit Egypt.
They were the latest in a series of assaults on Egypt's Coptic Christian minority, which makes up around 10 percent of the population of 92 million, who have been targeted by several attacks in recent months.
In December, a suicide bombing claimed by the Islamic State group killed 29 worshipers during Sunday mass in Cairo.
A spate of attacks in Egypt's restive Sinai Peninsula, including the murder of a Copt in the city of al-Arish whose house was also burned, have led some Coptic families to flee their homes.
About 250 Christians took refuge in the Suez Canal city of Ismailiya after the Islamic State released a video in February calling for attacks on the religious minority.
Fighting between Egyptian forces and the local Islamic State affiliate the Sinai Province has escalated since Egyptian President Abd al-Fattah al-Sisi took power from Muhammad Morsi of the Muslim Brotherhood in 2013.
Al-Sisi has come under attack over his violent suppression of Muslim Brotherhood members following his rise to power, which al-Sisi has argued is necessary to deter future attacks in the Sinai and across Egypt.