A three-metre barbed wire fence and the winding Tumen River are all that separate Nanping in China from North Korea, and after a spate of murders - allegedly by frontier-crossing intruders - frightened villagers are increasingly keen to leave, fearing neither the water nor the barrier are enough to protect them.

Over the past year at least 10 people have been killed by North Koreans -- mostly soldiers -- attempting robberies in the area, according to Chinese officials and state-controlled media reports.

Food security is a perennial issue in North Korea, raising the spectre of individuals driven by desperation to attack their wealthier neighbours in China.

Officially Nanping's population is more than 6,000, but in reality it is becoming a ghost town. Most houses and buildings have been abandoned for years, many with broken windows and overgrown gardens.

Its people are ethnic Koreans and the younger generation's multilingual abilities give them far better employment opportunities with South Korean firms elsewhere.

All have left, leaving only the elderly and a small Chinese military contingent, along with local Communist Party secretary Wu Shigen, who is in his 30s and said he was by far the youngest person in the village.

He has a two-pronged plan for keeping the peace: a voluntary curfew and an information blackout.

"I tell all the residents not to go out at night, and to pay attention to their safety," Wu said -- although most of those killed were murdered in their homes.

"There are no witnesses for any of these attacks and we don't tell the residents much," he added. "The less people know, the less they will be afraid."

Security cameras watch the two streets running parallel to the border and China earlier this year announced civilian-military patrols for the area.

However, residents said the militia was never set up, with a shop owner adding some elderly villagers have joined the exodus in recent months, scared away by the violence.

- Longstanding allies -

In April, a trio of North Korean soldiers searching for food and money killed three people near Nanping, according to local authorities and Chinese media.

That came after a North Korean soldier was fatally shot in December having murdered two elderly village couples while stealing 100 yuan ($16) and some food, they said.

China's foreign ministry spokesman Hong Lei said after the quadruple killing that it had "lodged representations" with Pyongyang and both sides took the case "very seriously", adding the North had "expressed its regret that such (an) incident happened".

It was a rare open censure of a longstanding ally.

Three months earlier a North Korean civilian was captured after killing a family of three during a robbery, the Beijing News reported, also confirmed by officials in the area.

Beijing's willingness to publicise the deaths may reflect frustration with North Korean authorities, analysts say, pointing out there may have been earlier murders that were not disclosed at the time.

The two Communist countries have long been partners, their ties forged in fire when Beijing sent more than a million troops to fight for Pyongyang in the Korean War.

It remains the North's main diplomatic protector and aid provider.

At the same time it fears instability and nuclear-armed North Korea has long oscillated between conciliatory offers and blood-curdling threats against its enemies, while leader Kim Jong-Un himself has yet to visit Beijing.

- End of the line -

Although North Korea's military enjoy a privileged position and first call on its limited resources, those posted along the sleepy frontier towns may still be struggling to survive.

Any border guard illegally crossing into China must be in dire straits, said Scott Snyder, a senior fellow at the Council on Foreign relations, as they face execution if returned to North Korea.

"Within North Korea's distribution system, the farther away you are from Pyongyang or other large concentrations of people, it's the end of the line," Snyder added.

"These soldiers may not be getting what they need due to corruption, inefficiency, system failures, and probably a combination of all those."

In Nanping, surviving captives are handed to China's People's Liberation Army, Party secretary Wu said, adding: "I don't know what happens to those North Korean soldiers. The military deals with them."

Local Chinese army officers declined to discuss their fate.

According to Seoul-based website DailyNK, the head of Pyongyang's General Bureau of Security, which guards the North Korean side of the border, was dismissed along with three regional commanders over last year's killings.

Relations on the ground used to be much closer.

Beijing's policy is to repatriate any fleeing North Koreans, who have to pass through China to reach third countries and travel on to the South.

But tens of thousands escaped to China during famines in the 1990s and 2000s, and were once greeted warmly, and with gifts of food, by their ethnic kinfolk.

"That was before," said a grocer surnamed Cai. "Now maybe it's better for them to stay on their side of the border."