China did not export any crude oil to North Korea in the first three months of this year, data compiled by South Korea's government trade agency showed Thursday, in an unprecedented three-month absence of oil shipments amid North Korea's threats of a nuclear test. Monthly shipments of crude oil from China to North Korea were absent in February, June and July last year, but it was the first time that China apparently stopped exports of crude oil to North Korea for three consecutive months. The Beijing unit of the South's Korea Trade and Investment Promotion Agency (KOTRA) said in a report, citing data it collected from China's customs authorities, that there were no oil shipments from China to North Korea from January to March this year. "To my knowledge, it is the first time that China did not export crude oil to North Korea for three consecutive months and that would impact the North Korean economy," a diplomat at the South Korean Embassy in Beijing said on the condition of anonymity. China's total trade with North Korea fell 2.83 percent to US$1.27 billion in the January-March period, compared with the same period a year ago, according to the KOTRA report. China, the North's main ally and economic lifeline, issued a veiled warning on Wednesday to North Korea not to conduct its fourth nuclear test. "We are opposed to all actions that may lead to an escalation of tensions on the Korean Peninsula," China's foreign ministry spokesman, Qin Gang, told reporters during a regular press briefing, when asked about the possibility of a new nuclear test by North Korea. "We should cool down the situation, rather than flaring up tensions," Qin said, adding that China was paying "high attention" to reports that said heightened activities have been detected at North Korea's nuclear test site of Punggye-ri.