Fire has destroyed one of China's oldest cathedrals which had been placed under government  protection, a State media report says.

More than 50 firefighters tried to salvage the 142-year-old Jiangbei Sacred Heart Church in the eastern sea port of Ningbo early on Monday, the Xinhua news agency reported.

Nuns living nearby said they heard a noise at the cathedral and discovered the fire just after midnight, said parish priests Rev. Xavier Jin Yangke, ucanews reported.

"When they opened the door to inspect they discovered that the church was on fire and reported it to the police immediately," he said.

The fire raged for more than two hours before firefighters extinguished the flames which gutted the interior and the roof of the church.

Only the frame of the main building, the bell tower and nearby buildings within the church complex remained as the interior of the church was gutted, a firefighter said.

"The inside of the building is totally destroyed. It's a great loss. The church is such a beautiful building," one of the firefighters told Xinhua.

The Gothic-style cathedral was a Ningbo landmark built by French missionary priests in 1872.

The Communist Party granted the structure State protection after it served as a party revolutionary base. It has since been declared as a national monument.

The last time the cathedral sustained major damage was during the Cultural Revolution from 1966 to 1976. Authorities gave back control of the cathedral in the 1980s.

Investigators were on Tuesday piecing through evidence as to how the fire started.

Nuns living nearby said they heard a noise at the cathedral and discovered the fire just after midnight, said parish priests Rev. Xavier Jin Yangke, ucanews reported.

"When they opened the door to inspect they discovered that the church was on fire and reported it to the police immediately," he said.

He told ucanews.com that he and some companions inspected the cathedral upon hearing the noise and they saw that the church was on fire.

One of the cathedral's staff who stayed inside the church told investigators that the fire started at the altar, Xinhua reported