South Korea believes 300 of its veterans are still alive in the North

The 72-year-old man, Jeon Yong-il, was detained in eastern China along with his wife when they tried to use forged passports to fly to South Korea.

The South Korean embassy in Beijing has called on China to release the couple.

South Korea believes up to 300 Korean War prisoners are still alive in the North, but very few manage to escape.

We hope the Chinese authorities will send him to South Korea as soon as possible S Korean embassy official

"He is a South Korean national and a war prisoner. There is no doubt about that. We've proven his case," said a South Korean embassy spokeswoman.

"We hope the Chinese authorities will send him to South Korea as soon as possible," she said.

Mr Jeon and his wife were arrested by the Chinese authorities on Monday last week, while they were trying to board a Seoul-bound plane in the city of Hangzhou.

It is believed they had been in China for several weeks after crossing the border from the North.

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Early reports suggested that they had been sent to a detention camp near the North Korean border, raising fears they would be sent back to the North.

But South Korea's Yonhap news agency said it was unlikely the Chinese would send him to North Korea because they had identified him as a Korean War prisoner from the South.

Mr Jeon's case has been held up because he was not on the South Korean Defence Department's list of prisoners of war. He was on the killed-in-action list.

But the embassy official said they had studied photographs and confirmed it was the same man.

Mr Jeon joined the South Korean army in 1951 at the age of 19, one year after the war broke out.