North Korea's military said the launches were simulated strikes on South Korea and the United States, criticising their joint air exercises as an "dangerous, aggressive war drill."
Pyongyang has been carrying out weapons tests at an unprecedented pace this year, firing a short-range ballistic missile and hundreds of artillery rounds near the heavily armed inter-Korean border.
North Korea has never confirmed how many people caught COVID, apparently because it lacks testing supplies. Instead, it has reported daily numbers of patients with fever, a tally that rose to some 4.77 million.