If South Korea is found to have done anything wrong, the government will immediately apology and address the problem, he said.

The offer is the latest in South Korea's response to Japan's export restrictions against the neighbor on three types of key chemical materials used in memory chips and smartphones -- fluorinated polyimides, photoresist and hydrogen fluoride, also known as etching gas.

The Moon administration initially sought to respond calmly to the trade measure, which took effect last week, with a focus on a diplomatic resolution.

But it has shifted to a rather tough mode, as Japanese officials have "groundlessly" linked the export curbs with UN sanctions against Pyongyang.

They openly questioned whether South Korea is trustworthy in handling the imported strategic materials. Some Japanese media also reported rumors of the materials being smuggled out of South Korea on multiple occasions partly in breach of UN resolutions.

Seoul has dismissed Tokyo's claim as a politically charged campaign to justify its export control, an apparently retaliatory measure over historical issues.

Kim expressed "strong regret" that Japanese leaders are making "irresponsible" comments deliberately indicating loopholes in South Korea's strategic material control and UN resolution implementation.

Over the past four years, Kim pointed out, South Korea caught more than 150 attempts to export such materials without authorization. The government made an announcement on that as well.

It demonstrates that South Korea is abiding by global export control rules strictly and transparently, he added.

If it's proved that South Korea is innocent, Japan will have to offer an apology itself and immediately withdraw the export restrictions, he said.

Kim, who's doubling as head of the secretariat of the National Security Council, urged Japan to ask itself if it's transparently following the four export control systems: the Wassenaar Arrangement, Nuclear Suppliers Group, Australia Group and Missile Technology Control Regime.

He called for a full investigation into possible violations by Japan as well.

Another Cheong Wa Dae official said the government will first wait for Japan's response and consider a next step if necessary.

"Now that the Japanese side says it can't trust (us) and talks about (alleged) smuggling cases, we are telling them 'let's go through a probe (together),'" the official told reporters in a background briefing.

Cheong Wa Dae's proposal is that the UN Security Council's Panel of Experts or another "appropriate" international agency look into relevant activities by both South Korea and Japan, according to the official.

On news reports that Russia can be an alternative supplier of etching gas for South Korean firms, the official confirmed that the Russian government has made an offer.

"Currently, the issue is under review," the official said. (Yonhap)