That is roughly equal to the 520,000 tons estimated by the Korea Trade-Investment Promotion Agency (KOTRA) as the amount China is sending to the North via pipelines between Dandong and Sinuiju.
The boss of one seafood trading company told the South China Morning Post earlier that business had slowed since the ban, but some traders were entering the North Korean trade zone during evening high tide and loading up with seafood before returning to Dandong.
He called on anyone aware of efforts to enable North Korean trade to come forward before getting caught, warning: "We are closing in on North Korea's trade representatives".
The new measures banned textile exports and capped fuel imports.
"It puts North Korea on notice that should they continue on this course, that the maximum sanctions initially proposed are still on the table and could invariably be imposed", said Roh.
"The world will witness how (North Korea) tames the USA gangsters by taking a series of actions tougher than they have ever envisaged", the foreign ministry said in a statement carried by the official KCNA news agency.
The Democratic People's Republic of Korea (DPRK) is "ready to use a form of ultimate means", Mr Han said, without elaborating.
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China, which provides most of the oil to North Korea and wields a security council veto, has opposed such a move.
Chinese officials have privately expressed fears that an oil embargo could risk causing massive instability in its neighbour.
The United States and its allies argue that tougher sanctions will pile pressure on the regime of Kim Jong-Un to negotiate an end to its weapons programme but experts are sceptical about whether they will curb Pyongyang's nuclear drive.
US Treasury Secretary Steven Mnuchin warned China that if it did not follow through on the new sanctions, the United States would "put additional sanctions on them and prevent them from accessing the US and global dollar system".
The head of Senate Armed Services Committee said Washington should strengthen its missile defenses in South Korea while putting more pressure on China to stop the North's development of nuclear weapons and ballistic missiles.
The latest resolution contained new political language urging "further work to reduce tensions so as to advance the prospects for a comprehensive settlement".
Liu said relevant parties should resume negotiations "sooner rather than later".
It also bans joint ventures with North Korean entities, except for non-profit public utility infrastructure projects.