Over 50 Christian homes and a Catholic school are among the buildings that have been badly damaged by airstrikes in Gaza.
The Rosary Sisters School catered for 1,250 students, both Christian and Muslim, from impoverished communities.
Speaking to Catholic charity Aid to the Church in Need (ACN), the school's principal, Sister Nabila Saleh, said she was "heartbroken" by the destruction of the school.
"Everything is ruined. It is very sad," she said.
The school had already been evacuated at the start of the conflict and the sister understands that no one was killed in the air strike.
ACN expressed its own sadness that an aid project that had already been approved for the school can no longer go ahead.
The nuns have decided to stay where they are instead of evacuating so that they can continue to care for people in need.
They include many Christians who are sheltering at the Holy Family Church and the Orthodox Church of St Porphyrius, despite supplies running dangerously low.
They are caring for over 750 displaced Christians, including 100 children and 70 people with special needs.
A source who cannot be named for security reasons said: "The fighting is coming closer and closer.
"But without a humanitarian truce there can be no evacuation because people are very scared – they are hearing about bombing in other areas in the Gaza Strip.
"Moreover, famine and lack of water and shelter are terrible in these other areas as well."
According to the Orthodox Patriarchate of Jerusalem, 19 places of worship, including mosques and churches, were attacked in Gaza during the first three weeks of the conflict.
"In times of crisis and adversity, we turn to the words of Psalms 34:18, which remind us that 'the Lord is close to the broken-hearted and saves those who are crushed in spirit'," it said in a statement.
"We pray for peace, justice, and a swift end to the suffering in Gaza."
One of the buildings hit was the Orthodox Cultural Centre. The ACN partner said: "The centre, which was built after 12 years of hard work, was totally destroyed."