China is nervous about a nuclear armed North Korea.
But customs administration spokesman Huang Songping said Beijing was upholding the United Nations sanctions against the regime of Kim Jong-Un.
That increase "cannot be used as evidence questioning China's seriousness in fulfilling UNSC resolutions", Huang said.
He pointed to a 13.2 percent drop in imports from North Korea in the same period as an example of the pressure, adding that there have been sharp decreases every month since March.
"Make no mistake, the Security Council's sanctions on [North Korea] can not be equated with all-encompassing economic sanctions".
"Trade related to the people's livelihood in North Korea, especially if it embodies humanitarian principles, should not be affected by sanctions", said Huang at a separate news briefing.
The decline follows China's decision in February to ban all imports of North Korean coal.More news: With Shares Trading up at $11.64 (MTG) MGIC Investment Corporation Schedules…
The overall rise in trade has been driven by China's exports to North Korea, which were up by almost 30% in the first half of the year.
The price of gasoline sold by private dealers in Pyongyang and the northern border cities of Sinuiju and Hyesan jumped to $2.18 per kg ($2.92 per liter) as of July 5, up 50 percent from $1.46 per kg on June 21, according to Reuters analysis of data collected by the Daily NK website.
The North has conducted two nuclear tests since the beginning of previous year and missile-related activities at an unprecedented pace.
The White House took swift action after seeing that a strategy of persuasion wasn't working - approving a long-delayed arms sales package to Taiwan, sending in a pair of freedom of navigation operations to challenge Beijing's territorial claims in the heavily contested South China Sea, and imposing an initial round of secondary sanctions, which targeted a few individuals and companies with financial ties to Pyongyang.
The US ambassador to the UN, Nikki Haley, said on Sunday that Washington would crank up pressure on China to ensure it implements sanctions over the missile test.
"We're going to push hard against China because 90 percent of the trade that happens with North Korea is from China, and so while they have been helpful, they need to do more", she told CBS television.
The government is likely North Korea's largest user of fuel products, but most gasoline and diesel bought by ordinary citizens comes from private dealers and smugglers, experts say.