It comes after the rapidly spreading disease has ravaged farms in China, where more than a million pigs have reportedly been culled, and spread to Vietnam, Cambodia and Mongolia in recent months.
The disease is harmless to humans but is fatal and highly contagious for pigs and there is no known cure or vaccine.
Oh Soon-min, director of quarantine policies at South Korea’s agriculture ministry, said quarantine measures and blood tests will be stepped up in 350 pig farms near the Korean border.
Fences and traps will also be installed near the farms to prevent the pigs from coming into contact with wild boars that roam in and out of North Korea.
Mr Oh said: “While North Korea’s Jagang province, where the outbreak of the African swine fever was confirmed, is near the border between North Korea and China, we do believe this is a serious situation as there is a possibility that the disease can spread towards the South.”
He added that South Korea’s capital Seoul believes the North raises about 2.6 million pigs in 14 government-run or co-operative farms.
The South hopes to discuss the issue with North Korea at an inter-Korean liaison office and find ways to help fight the spread, according to Lee Eugene, a spokeswoman from Seoul’s Unification Ministry.
The outbreak comes as the North has significantly slowed its engagement with South Korea following the collapse of a February summit between North Korean leader Kim Jong Un and US president Donald Trump.
Ms Lee said the South had told Pyongyang "several times" that it could help in case of an African swine fever outbreak, but did not confirm how North Korean officials responded.
Associated Press contributed to this report.
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