North Korea has test-fired two short-range missiles off its west coast, South Korean officials say.
They are believed to be ground-to-ship or ship-to-ship missiles with a range of some 100km (60 miles), they say. They landed in North Korean waters.
Pyongyang test-fired at least one short-range missile at the end of May - off its east coast - as part of what appeared to be military exercises.
North Korea's military programme is a major source of international concern.
"I believe North Korea launched two missiles into the West Sea today [Thursday] - one in the morning and the other in the afternoon," a South Korean intelligence official is quoted as saying by South Korean news agency Yonhap.
Thursday's suspected test off the west coast may have been carried out after a similar test failed on 25 May, when the North test-fired missiles off the east coast, a South Korean official was quoted as saying earlier.
"It's seen as the North firing the missile that it didn't launch at that time," he said.
The US condemned the launches, describing them as "not constructive".
"The United States and our allies believe that North Korea should refrain from testing missiles," said National Security Council spokesman Gordon Johndroe.
The North "should focus on the denuclearisation of the Korean peninsula and fulfil its obligations" under a February agreement to close down its only nuclear reactor, he added.
South Korea confirmed at least one missile was test-fired into the Sea of Japan on 25 May, although earlier reports suggested several had been fired.
It coincided with the launch of South Korea's first destroyer equipped with US-supplied high-tech Aegis radar.
Despite international alarm at the North's long-range missile and nuclear tests last year, the US and Pyongyang's regional neighbours played down the May test.
The US state department described it as a "routine exercise" that would not affect six-party talks regarding the North's nuclear programme.
The tests come weeks after the North missed the February deadline to shut down its Yongbyon nuclear reactor in return for economic and energy aid.
Pyongyang has refused to move forward on the deal until it has access to North Korean funds in a Macau bank, which had been frozen amid claims the money was linked to counterfeiting and money-laundering.