North Korean children are risking their lives to escape harsh conditions in their homeland, Release International has warned.

According to Release partners in China, a 13-year-old North Korean boy was recently found hiding in the mountains in freezing temperatures after escaping over the border. He had to have both his feet amputed as a result of severe frostbite and is now being cared for in a safe place.

According to the organisation, which supports persecuted Christians worldwide, the Chinese authorites are intensifying efforts to repatriate defectors, including children. As a result, many of them are going into hiding rather than face the prospect of being returned to North Korea.

Security has been tightened along the North Korea-China border since the death of Kim Jong Il, increasing the risk for North Koreans attempting to flee their country.

"Our concern is that the Chinese and North Korean authorities are working together to try to root out networks providing support for refugees fleeing to China," said Release.

"And we fear they will redouble their efforts in the period leading up to April 15, which is the 100th anniversary of the birth of Kim Il Sung.

"Along with many others, we call on China to drop its cruel policy of repatriating people – including children – who are genuine refugees."

Release supports a Seoul-based ministry helping refugees. Many become Christians, and some return at great risk to their homeland to share the gospel.

A petition signed by 52,000 people was recently presented by the organisation to the North Korean embassy in London calling upon new leader Kim Jong-un to stop the persecution of Christians.

"Because of their faith Christians are detained in camps, brutally tortured and removed from society," Release continued.

"Many are forced to flee their country to avoid terrible persecution and oppression."