North Korea has imposed a lockdown in Kaesong city, claiming that the country’s first suspected case of the coronavirus has been discovered there, AFP reported on Sunday. Kaesong city borders South Korea.

The news agency quoted the official Korean Central News Agency as saying that a defector who had left for South Korea three years ago returned after illegally crossing the border on July 19, but brought the coronavirus with him. State media said the patient has been put under “strict quarantine”, as has anyone who has come into contact with him. KCNA said it was a “dangerous situation...that may lead to a deadly and destructive disaster”.

North Korean officials said that “severe punishment” will be given to those who are responsible for letting the man cross the border, BBC reported. But South Korea has not reported any incidents of border crossings into the North.

North Korean leader Kim Jong-un convened an emergency meeting of the Politburo on Saturday to implement a “maximum emergency system and issue a top-class alert” to contain the virus. Kim was quoted as saying that “the vicious virus could be said to have entered the country”.

Pyongyang has so far denied that there are any cases of the virus in the country. North Korea completely closed its borders in January, and imposed a tough lockdown. Earlier this month, Kim said the country will keep its borders closed “for the foreseeable future”. Kim had also celebrated his country’s “shining success” in keeping the coronavirus out.