North Korean border guards shot dead five refugees and wounded two others after pursuing them across the frontier into China last month, a South Korean newspaper reported Tuesday.

The incident happened near the North's northeastern city of Hyesan on December 14 after the refugees crossed the frozen Yalu border river, Chosun Ilbo newspaper said, quoting a source in China.

It said border guards chased them and opened fire on the Chinese side. They dragged the bodies and the wounded back across the border with the acquiescence of Chinese authorities.

Chosun Ilbo said it was the first time the North's guards had shot at refugees who had already crossed the frontier.

It said Kim Jong-Un, son and heir apparent to leader Kim Jong-Il, has ordered soldiers to shoot anyone who tries to cross the border without permission.

The South's National Intelligence Service declined to comment on the report.

Open Radio for North Korea, which broadcasts into the North, said Kim Jong-Un on January 3 called for a crackdown on North Korean escapees living in China.

The directive was in response to an official complaint from Chinese security authorities that the refugees are a burden on security, the radio quoted an informed source as saying.

Kim Jong-Un has denounced the refugees for undermining the communist state's ideological foundations, it added.

Tens of thousands of North Koreans who fled hunger and poverty at home are believed to be leading a precarious life in China as illegal immigrants. If found, they are returned to the North for probable harsh punishment.

China treats them as economic migrants rather than refugees, a policy criticised by rights groups.