South Korean priests have celebrated mass in North Korea's capital after some of the families split by the war were reunited after over 60 years.

A delegation of 12 priests from the Association of Catholic Priests for Justice (CPAJ) were invited by the government controlled Association of Catholics of the North for a five day visit to Pyongyang, Fides reports. The visit was the first by a Catholic delegation since 2008.

The celebration of the mass was offered for the reunification of the two Koreas.

This move could lead to visits by other groups of the civil society, "in the logic of promoting exchange of a religious type not political", said an official of the South Korean government, who authorised the visit.

The fact that this trip was given permission is surprising given North Korea's record with religious freedom and human rights. Open Doors, an organisation which campaigns on behalf of persecuted Christians, regularly places North Korea at the top of its World Watch List of countries where religious freedom is severely restricted. Given the atrocities against Christians committed by Islamic State in the Middle East, it speaks volumes that North Korea remains ahead of Iraq and Syria as a more difficult place to be a Christian, according to Open Doors.

Although evangelism carries the risk of the death penalty or imprisonment in labour camps, there are an estimated 300,000 Christians living in secret in North Korea.

Open Doors tells the story of a woman called Chun, who was sent to one of North Korea's horrific labour camps after she tried to escape to China as punishment for 'defecting' (refugees who do reach China are often sent back).

"I was beaten and tortured so badly that I could barely stand up," she said. However, in her dirty, overcrowded prison cell, she recalled, "There was one lady who was really kind to me. When I was in so much pain she invited me to lay my head in her lap. She stroked my hair."

"This lady came to faith when she was in China. She was put behind bars, just like me. It did not stop her from doing Christ's work."

Some time later Chun herself became a believer. She said, "Despite all my suffering I love God with my whole heart. I am so grateful for him."

This week's visit comes after 100 families who were divided after the 1953 Korean Armistice Agreement were offered the chance of a brief meeting. The reunions were part of a deal negotiated between Seoul and Pyongyang.

The families, many of whom have not had any contact with their relatives for over 60 years, were able to meet briefly under the close watch of North Korean guards.