Mr Wang's comments came a day after South Korea's military fired warning shots at an unidentified object from North Korea on Tuesday.
The South Korean Joint Chiefs of Staff issued a statement that the country was "keeping a full military readiness".
The administration of US President Donald Trump has said military action was an option under consideration, sending fears of conflict spiralling. It provided no other details.
In this Monday, May 22, 2017 photo, South Korean army's K-55 self-propelled howitzers fire during the annual exercise in Paju, near the border with North Korea, South Korea.
China has been infuriated by the USA deployment of its Terminal High Altitude Area Defense (Thaad) system in South Korea, saying it is a threat to its own security and will do nothing to ease tensions with North Korea.
Last Friday, North Korea's deputy U.N. ambassador Kim In Ryong told U.N. correspondents that the government will rapidly strengthen its nuclear strike capability as long as the United States maintains its "hostile policy" toward the country.
South Korea's Yonhap news agency, without citing a source, reported that the South fired about 90 machine gun rounds into the air and toward North Korea. Most recently, a North Korean defector sent leaflets containing information about the murder of Kim Jong-nam, believed to be the work of North Korean assassins, across the world's most heavily-guarded border.More news: Lawyer Says Kushner Willing to Cooperate With Investigators
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South Korea has been alarmed by several ballistic missile tests by Pyongyang, with the latest being the launch of a new intermediate-range solid-fuel rocket, conducted Sunday.
It "immediately went towards the North", a South Korean official said at the time.
Lee Min Bok, a North Korean defector-turned-activist, told AFP that cylindrical balloons made of plastic cost much less than round rubber ones.
The missile reportedly flew 310 miles, which places Japan and South Korea in the line of fire.
North Korea has in recent years touted its drone program, a relatively new addition to its arsenal.
Such tests present a hard challenge to new South Korean President Moon Jae-in, a liberal who took office on May 10 and has expressed a desire to reach out to North Korea.
In 2014, South Korean officials discovered what they described as several North Korean drones that had flown across the border.