Armed Chinese civilians patrol border with North Korea...........

Surveillance cameras, armed civilian patrols and an emergency hotline are among security measures being hurriedly introduced in Yanbian, a Chinese prefecture bordering North Korea, following a spate of murders by rogue soldiers from across the border.

An unnamed North Korean base, located within eyesight across the frozen Tumen river, may be responsible for as many as 20 killings, one official told the Beijing News. Military newspaper China Defence News, which reported the developments, described the situation as "complicated."

With the country's persistent food insecurity affecting rations, patrolling the porous, 880-mile northern border is usually considered a plum job by North Korean military personnel, thanks to contraband goods and bribes offered by smugglers in and out of China.

But the situation appears to have worsened following Kim Jong-un's dramatic purge of senior officials, including his uncle Jang Song Thaek, who had spearheaded commercial ties with China.

Relations between the two nominal allies have remained testy since Jang's execution, even as North Korea's continued nuclear ambitions have increased tensions in the region.

Analysts say Beijing has reduced some cross-border trade and aid shipments as a sign of displeasure, while President Xi Jinping's state visit to South Korea was seen as a deliberate snub to its northern ally.

The response to the border incursions suggests a leadership with dwindling faith in its counterparts in Pyongyang.

"It's difficult to rely on just one party in maintaining effective control," China Defence News explained diplomatically.

In one high-profile incident last month, a deserter shot and bludgeoned two elderly couples to death in "an apparent robbery," South Korea's Yonhap agency reported, before being captured or shot.

The incident prompted an official complaint from China, while details were leaked to media despite an alleged agreement to cover-up the killings.

Many of Yanbian's younger villagers have already migrated in search of work, while others have fled the deadly raids. They leave behind an older, ethnically Korean population, easily preyed upon by desperate guards seeking food and money.

In September, three family members were beaten to death for 500 yuan by a North Korean civilian who was later caught at the border, a relative told Bloomberg, adding he was given 3,000 yuan in compensation.

In 2013, another defector robbed and killed a couple.

China's Global Times interviewed one restaurateur in the port city of Dandong who disturbed an armed man pilfering in the middle of the night.

"He sped away by boat, taking some bits of meat with him," the man said.