South Korea's chief nuclear negotiator Lee Do-hoon met separately with the top Chinese and Russian envoys to Seoul on Friday and discussed the situation on the Korean Peninsula.

The meetings took place as Lee reported to work for the first time since his release from mandatory two-week self-isolation after returning from a trip to Washington, where he held talks with his counterpart, Deputy Secretary of State Stephen Biegun.

Lee first met with Chinese Ambassador Xing Haiming, who was seen arriving at the foreign ministry in the afternoon. When approached by reporters with a question on what he would be discussing with Lee, he said he came to discuss "the situation on the Korean Peninsula."

A couple of hours later, Russian Ambassador Andrey Kulik was spotted entering the ministry.

"I'll discuss the Korean Peninsula issue with Special Representative Lee," he told reporters. "The security issue in this region is very important for us too."

Tensions between the two Koreas spiked sharply last month, as the North cut off cross-border communication lines, blew up an inter-Korean liaison office and threatened to take military action in anger over anti-Pyongyang propaganda leaflets.

But the situation later cooled off slightly after leader Kim Jong-un put military action plans on hold.

Friday's meetings between Lee and the ambassadors also came amid news reports that Biegun is planning to visit South Korea next week.

The nuclear negotiations between Washington and Pyongyang remain at an impasse after the collapse of the Hanoi summit of US President Donald Trump and leader Kim. They failed to reach a deal on the scope of the North's giving up of its nuclear weapons program in return for US concessions. (Yonhap)