In previous years, China's official shipments of crude oil to North Korea had been absent for several months, particularly after the North's nuclear tests. However, it was extremely unusual that, at least on paper, China sold no crude oil to North Korea for all of last year.

In 2014, China's exports of petroleum products to North Korea jumped 48.22 percent from a year earlier to US$1.54 million, according to the data based on Chinese trade statistics and compiled by the Beijing unit of South's Korea Trade and Investment Promotion Agency.

"Although final statistics show that China's exports of crude oil to North Korea were counted as 'zero' in 2014, experts suggest that the possibility of China's suspension of crude oil exports to North Korea remains low," the agency said in a statement.

South Korean diplomatic sources in Beijing have also cautioned against reading too much into the official Chinese trade figures because China has provided crude oil to North Korea in the form of grant aid and such shipments were not recorded on paper.

There has been no clear indication that the 2014 trade figures reflect China's willingness to use crude oil as leverage to press North Korea to change course in its nuclear ambition.

North Korea conducted its third and most powerful nuclear test in February 2013, straining political ties with Beijing's leadership.

Asked about the absence of crude oil shipments to North Korea, Chinese foreign ministry spokeswoman Hua Chunying stressed Beijing's "normal" trade relations with North Korea, but sidestepped questions over whether Beijing genuinely stopped shipping crude oil to Pyongyang.

Excluding crude oil, bilateral trade between North Korea and China fell 2.79 percent from a year ago to $6.36 billion last year, marking the first annual decline in six years, according to the data. (Yonhap)