Nearly 22,000 pigs have been culled since the outbreak was first confirmed last week in the border towns of Paju and Yeoncheon, but officials have yet to identify the infection route.
North Korean leader Kim Jong-un oversaw the test of a "super-large multiple rocket launcher", state news agency KCNA reports.
North Korea fired two "unidentified projectiles" into the sea off its eastern coast, South Korea's military says, the latest in a series of launches by Pyongyang.
North Korea said that inter-Korean talks are over, while reportedly launching at least two projectiles into the sea on Friday.
North Korea fired two unidentified projectiles into the sea, said South Korea, in the latest launch that came shortly after US President Donald Trump said he had received a "very beautiful letter" from North Korean leader Kim Jong Un.
North Korea's latest missile launches were meant as a warning to Washington and Seoul over their joint war games, the North's leader Kim Jong Un said, according to state news agency KCNA.
The test verified the combat effectiveness of the overall system, and North Korean leader Kim Jong-un predicted "it would be an inescapable distress to the forces becoming a fat target of the weapon", state news agency KCNA said.
Thursday's missile tests were the first since Kim and US President Donald Trump agreed to resume nuclear talks during an impromptu meeting last month in the demilitarised zone between North and South Korea.
"We urge the North to stop actions that do not help ease military tensions," said Choi Hyun-soo, a defence ministry spokeswoman for South Korea.
President Donald Trump becomes the first US leader to enter North Korean territory after meeting its leader Kim Jong-un at the DMZ.
At a time when "serious and complicated changes are happening in international and regional situations", KCNA said the two leaders agreed to "promote close strategic communication" and develop their "common interests".
Xi is the first Chinese president to visit North Korea in 14 years after relations between the Cold War era allies deteriorated over Pyongyang's nuclear provocations and Beijing's subsequent backing of UN sanctions.
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