An 1,500-year-old underground church has been discovered in Turkey with never-before-seen frescoes depicting Jesus and "bad souls being killed". The church was found in the world's largest known underground city in the Cappadocia region of central Turkey.

The frescoes have been described as depicting Jesus rising into the sky – known in Christianity as the Ascension – and the destroying of evil – known as the Last Judgement. The discovery of the church itself – which archaeologists suggest could be more than 1,500 years old – still has secrets to be revealed, as so far only the roof and uppermost part of the walls have been uncovered.

"Only a few of the paintings have been revealed," said researcher Ali Aydin, who told the Hurriyet Daily News: "There are important paintings in the front part of the church showing the crucifixion of Jesus and his ascension to heaven. There are also frescoes showing the apostles, the saints and other prophets Moses and Elyesa."

An urban housing project was taking place in the city of Nevşehir, where the church was found. It is part of a huge number of early dwellings, which form the largest known ancient underground city. The underground city itself was discovered in 2014, and around four miles of tunnels have been uncovered. The experts believe people lived here around 5,000 years ago.

Nevşehir'de Dünya Ortodoksluğu'nun tarihi akışına yön verebilecek eski bir kilise bulundu. https://t.co/MBGLYPIVEl pic.twitter.com/mvHCKMIxK2 — Kamu Diplomasisi (@BasbakanlikKDK) January 22, 2016

Archaeologists have had to pause their excavations, however, as the winter humidity can damage the paintings. However, they have managed to reveal the ceiling of the structure which mainly sits underground, and were fascinated by the huge frescoes which can be found across the inside of the roof and top of the walls.

"We know that such frescoes have so far never been seen in any other church," said Hasan Ünver, mayor of Nevşehir. "It was built underground and has original frescoes that have survived to this day. This place is even bigger than the other historical churches in Cappadocia.

"It is reported that some of the frescoes here are unique. There are exciting depictions like fish falling from the hand of Jesus Christ, him rising up into the sky, and the bad souls being killed. When the church is completely revealed, Cappadocia could become an even bigger pilgrimage center of Orthodoxy,."

Researchers hope to continue excavating the site in the spring. When it was first discovered, the church was filled with earth, and pieces of the painting had to be collected separately. Lead researcher of the church and underground city, Semih İstanbulluoğlu, said: "The structure was found a short time ago. The frescoes on the walls will return to their original look after restoration and cleaning work."