North Korea has expressed regret over the killing of four Chinese citizens by a runaway North Korea soldier late last month and the alleged perpetrator was shot dead during a manhunt, according to China's foreign ministry Thursday.

The North Korean soldier crossed into the Chinese border town of Nanping, just north of the Tumen River overlooking North Korea's North Hamkyong Province, and killed four elderly Chinese people on Dec. 28 last year during a robbery attempt.

China has lodged a rare diplomatic protest with North Korea over the killing, but appears keen to avoid further straining ties with its only treaty ally, Pyongyang, describing the border incident as "an individual criminal case."

"After the incident occurred, the Chinese police immediately launched a manhunt operation. During the operation, the killer was shot and died later after medical treatment failed to revive him,"

China's foreign ministry spokesman Hong Lei said in a statement posted on the ministry's website on late Wednesday.

"The DPRK (North Korea) side expressed its regret that such an incident happened, and conveyed its sympathy to the family of the victims," Hong said.

"This is an individual criminal case," Hong said, adding that the two nations have been "carrying out follow-up investigations and dealing with the case in accordance with the law."

It is not uncommon for North Korean soldiers or citizens to cross the border into Chinese towns and attempt robberies.

In December 2013, a North Korean defector in his 20s killed an elderly Chinese couple in the Chinese border city of Yanji and stole 20,000 yuan (US$3,210). The North Korean defector was caught by Chinese authorities after fleeing to Beijing. (Yonhap)