Although gasoline prices eased to $2.05 per kg by July 12, they are still more than double from the beginning of the year, when they were averaging just under $1 per kg, the data shows.
The South also proposed separate talks by the rival states' Red Cross organizations to resume a humanitarian project to reunite families separated during the 1950-53 Korean War in closely supervised events held over a few days.
Seoul's acting Red Cross chief Kim Sun Hyang said it wants separate talks at the border village on August 1 to discuss family reunions.
Foreign Ministry spokesman Geng Shuang said Chinese exports of iron to North Korea for civilian purposes do not relate to the sanctions targeting Pyongyang's nuclear and missile programs, and China will continue implementing the resolutions "in an all-out manner".
"We request military talks with the North on July 21 at Tongilgak to stop all hostile activities that raise military tension at the military demarcation line", South Korea's Vice Defence Minister Suh Choo-suk told a media briefing.
China insisted Thursday it was abiding by UN sanctions on North Korea despite a jump in its trade with the nuclear-armed nation that comes amid growing USA calls for Beijing to rein in its neighbour.
If the government meeting goes ahead, it will mark the first official inter-Korea talks since December 2015.
The Oct. 4 declaration was the outcome of the inter-Korean summit that was held in Pyongyang in 2007 between then South Korean President Roh Moo-hyun and then DPRK leader Kim Jong Il, father of the current leader Kim Jong Un.
The Koreas last convened for military talks in late 2014. But it remains to be seen whether the North will accept the proposal as it's still demanding South Korea repatriate twelve female North Koreans who defected to the South previous year. South Korea usually refers to loudspeaker propaganda broadcasts by both sides, while the North wants a halt to routine joint U.S.
Primary users of fuel products in North Korea include fishermen, farmers, truckers and the military.
By contrast, South Korea's population now stands at over 50 million, according to government statistics.
North Korea says the South abducted the 12 waitresses and the restaurant manager and has demanded their return, but the South has said the group made a decision to defect of its own free will.
It conducted the first test of an intercontinental ballistic missile (ICBM) earlier this month, claiming to have mastered the technology to mount a nuclear warhead on the missile.
Frustrated that China has not done more to rein in North Korea, the Trump administration could impose new sanctions on small Chinese banks and other firms doing business with Pyongyang within weeks, two senior USA officials said.