Wu Dawei arrives before a meeting with South Korean Foreign Minister Yun Byung-Se
North Korea marks several major anniversaries this month and often marks the occasions with major tests of military hardware.
The possibility of US military action against North Korea in response to such tests gained traction following last week's strikes against Syria.
Previously, Washington has leaned toward sanctions and pressure to deter North Korea, but comments from President Donald Trump's top aides at the weekend suggested that position may be hardening.
Yun Byung-Se and Wu Dawei shake hands
It probably is not realistic for the US to attack North Korea
Japanese defence ministry source
The US Navy strike group Carl Vinson canceled a planned trip to Australia and was moving toward the western Pacific Ocean near the Korean peninsula as a show of force, a US official said over the weekend.
The events took place after Trump and China's President Xi Jinping held a summit meeting in Florida, where Trump pressed his counterpart to do more to curb North Korea's nuclear programme.
China is North Korea's main diplomatic and economic ally.
South Korea said the focus remained on deterrence and readiness
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There were no immediate details on what was discussed between China's Special Representative for Korean Peninsula Affairs, Wu Dawei, and his South Korean counterpart.
But the talks were expected to focus on the North's nuclear issue, the South Korean foreign ministry said earlier.
It was also the first visit to South Korea by a senior Chinese official since the planned deployment of the US THAAD missile defense system led to a diplomatic row between Beijing and Seoul.
US Secretary of State Rex Tillerson said the US military strike against Syria over its use of chemical weapons was a warning to other countries including North Korea that "a response is likely" if they pose a danger.
Mr Wu is expected to discuss the North's nuclear issue with Yun Byung-Se
Mr Tillerson said on CBS's Face the Nation: "(Chinese) President Xi (Jinping) clearly understands, and I think agrees, that the situation has intensified and has reached a certain level of threat that action has to be taken."
North Korea has sounded a note of defiance, calling the US strikes against Syria on Friday "an unforgivable act of aggression" that showed its decision to develop nuclear weapons was "the right choice".
In Tokyo, the feasibility of U.S. military action was downplayed, while South Korea said the focus remained on deterrence and readiness.
A Japanese defence ministry source said: "It probably is not realistic for the US to attack North Korea.
"If America says it is going to attack, both Japan and South Korea will probably put a stop to it."
Mr Tillerson said the US military strike against Syria was a warning to other countries
A senior Japanese military source added: "If the US military was to attack, there could be a request to Japan for rear-guard logistics support but there has been no talk of such preparations."
South Korean and US forces are also involved in annual joint military drills that run until the end of April.
The North calls the drills preparations for war against it.
Several North Korean anniversaries in April could be an opportunity for Pyongyang to conduct nuclear or missile tests, South Korean defence ministry spokesman Moon Sang-kyun said.
North Korea has invited a large number of foreign media representatives to Pyongyang this week, likely to cover the so-called "Day of the Sun" birth anniversary on April 15 of the state founder Kim Il Sung.
Mr Moon did not directly respond to a question about the possibility of a US military strike against the North.
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He said: "Considering the possibility of North Korea's strategic provocations such as a nuclear test and missile launches, we have in place deterrence to the North's provocation and all readiness against them."
The Unification Ministry also played down the possibility of US military strikes against the North, saying it was confident Washington is fully behind the South's policy of using dialogue and pressure to resolve the North Korea situation, not force.
Senior envoys of South Korea, Japan and the United State on the North Korea nuclear programme will soon meet to discuss their coordinated response, the South's foreign ministry said.
North Korea launched a ballistic missile on Wednesday that flew a short distance before spinning out of control and crashing into the sea, the latest of a number of missile tests defying U.N. sanctions.
The North is also seen to be ready to conduct its sixth nuclear test at any time, with movements detected by satellites at its Punggye-ri nuclear test site.