North Korea launched "multiple unidentified projectiles" on Wednesday, South Korea's Yonhap news agency reported, days after firing two missiles as a warning over Seoul's plan for military drills with the United States.
"The projectiles were launched from the Hodo peninsula in South Hamgyong Province on the country's east coast," Yonhap said, citing South Korea's Joint Chiefs of Staff.
There was no confirmation from Pyongyang of the launch.
North Korean leader Kim Jong Un had said the two missiles fired last week under his personal supervision were a "solemn warning" over the military drills planned in South Korea with the United States, and that the missiles were newly designed tactical weapons.
Last week's launch was the first since Kim and US President Donald Trump agreed to resume nuclear talks during an impromptu June meeting in the demilitarised zone between North and South Korea.
That working-level dialogue has yet to begin and even before the recent launches, Pyongyang had warned the talks could be derailed by Washington and Seoul's refusal to scrap the annual manoeuvres between South Korean and American soldiers.
However Trump later brushed off Kim's bellicose language, saying the North Korean leader was warning South Korea, not the United States.
"He didn't send a warning to the United States," said the president, who has repeatedly touted his relationship with Kim, considered one of the world's most repressive dictators. "They have their disputes, the two of them have their disputes."