However, diplomats and Vatican sources cautioned that the trip could be put in jeopardy or parts of it changed if the security situation worsened.

The pope is due to spend about 27 hours in the Egyptian capital Cairo on April 28-29, meeting with President Abdel Fattah al-Sisi, grand imam Sheikh Ahmed al-Tayeb and the country's Coptic Pope Tawadros.

Archbishop Angelo Becciu, the Vatican deputy secretary of state, told Italy's Corriere della Sera newspaper that the events on Sunday, however tragic, "could not impede the pope from carrying out his mission of peace."

Tawadros was leading a congregation at Mass in Alexandria's Saint Mark's Cathedral when it was attacked. He was not hurt. That blast in Egypt's second-largest city came hours after a bomb struck a Coptic church in Tanta, a nearby city in the Nile Delta.

"There is no doubt that the pope will carry out his intention to go," Becciu said.

The Vatican also sent several communiques about logistics to journalists due to accompany the pope on his plane, in another indication that the trip was still on.

However, a senior diplomatic source said "we will have to keep our finger on the pulse of the situation until the very last minute."

In another indication of deepening worries about safety, there is no indication of the venue for a number of meetings by the pope in the latest programme.

Both Vatican and diplomatic sources said a number of events might have to take place in one location, such as the presidential palace, so as to limit the number of times the pope would have to move around in the city.

Both of Sunday's attacks were claimed by the Islamic State, which has waged a campaign against Egypt's Christian minority, the largest in the Middle East.

Egypt's cabinet said on Monday a state of emergency would remain in place for three months.