Christians in North Korea are reporting that their situation has not changed under the leadership of Kim Jong-un.

North Korea has topped the Open Doors World Watch List of the 50 worst persecutors of Christians for 10 years in a row.

Open Doors USA says that although the communist country's new leader has experimented with light agricultural reform and is a fan of Mickey Mouse, he has not made "any essential changes" in the first year since his father Kim Jong-il's death.

The organisation, which supports persecuted Christians worldwide, said Kim Jong-un had increased the number of spies in China searching for Christians and organisations that help North Korean refugees.

Border patrols have been taken over by North Korea's National Security Agency, which has put pressure on captured smugglers to disclose information about Christians helping defectors.

Open Doors reports that some arrested Christians were tortured and then released in order to betray their brothers and sisters or to serve as bait.

"This is extremely tragic," says a Open Doors co-worker involved in ministry among North Koreans.

"It's so dangerous to help Christians who have been released by the government. Some have been tortured so severely they cannot walk anymore.

"Often we cannot help them because that would bring too much risk to us.

"We can pray for them. We know that Jesus will not leave them, nor forsake them."

North Korean authorities are also tightly controlling television, radio and mobile phones.

Open Doors said North Korean Christians were reporting that they felt just as isolated from the outside world as they had done under Kim Jong-il.

The organisation said there were no signs that Kim Jong-un would improve freedom of religion in the country, as Christians contacts there continue to report that there have been no change in their circumstances.

Jerry Dykstra, Open Doors USA Media Relations Director, said: "Scrutiny of the estimated 200,000 to 400,000 brave underground Christians inside North Korea has increased during the last year.

"Of the estimated 150,000 to 200,000 people living under horrific conditions in prisons, there are 50,000 to 70,000 Christians. Also, many North Koreans are chronically malnourished and unemployed.

"Christians who escape to China from North Korea are hunted down and expatriated to their country where they face prison and often death. Christian groups which help the refugees are also under more scrutiny.

"But we know that Christians living under the most brutal regime in the world will be celebrating the birth of Jesus Christ this Christmas - most of them only in their hearts."