According to the Bishop, between 20,000 and 30,000 Christians out of a Christian minority of 160,000 have fled already the once thriving commercial capital of the country.
Syrian Christians are regarded as one of the largest remaining populations of Christians in the region.
The Bishop is also concerned about the safety of two priests, kidnapped weeks ago, and whose whereabouts are still unknown.
Addressing a regional humanitarian meeting in Rome as a representative of the Caritas-Syria charity, Audo described to AFP the situation in the war-ravaged city.
Since the closure of Aleppo airport, the Bishop has been working from his office in Damascus, who confided that he has been advised not to travel to Aleppo because the road are unsafe.
Talking about the two young priests who were kidnapped more than a month ago, Bishop Audo said that ransoms of 15 million Syrian pounds or around $150,000 (116,000 euros) have been demanded for their release.
Bishop Audo is adamant that Pope Francis, the newly elected Catholic pontiff, will do everything in his power, to help the Christians in Syria.