North Korea Sunday test-fired a short-range missile off its east coast, its fourth in two days, despite pleas from South Korea and the UN to halt the launches.

The guided missile was fired into the Sea of Japan on Sunday afternoon, said a defense ministry spokesman without elaborating.

On Saturday, the North fired three short-range missiles off its east coast.

The North's short-range missile launches are not unusual but come at a time of heightened alert on the peninsula, following Pyongyang's February nuclear test.

The South and its US ally had earlier been watching for any test by the North of medium-range Musudan missiles. But a US defense official said early in May the two mid-range missiles had been moved from their launch site.

However South Korea's unification ministry, which handles cross-border relations, said the short-range launches also posed threats to the region and should be stopped at once.

"We find it deplorable that the North has not stopped provocative actions such as the launch of guided missiles yesterday," said unification ministry spokesman Kim Hyung-seok before the latest exercise.

"We call on the North to take responsible actions for our sake and for the sake of the international community."

UN chief Ban Ki-moon also called for Pyongyang to "refrain from" further missile tests. He said it was time for it to resume talks with the international community and reduce tensions.

Seoul military officials were quoted by Yonhap news agency as saying that the missiles may be KN-02 surface-to-surface weapons with a range of up to 160 kilometers, or rockets of at least 300 millimeters in caliber.

"Such a stern response must have baffled the North greatly and Kim Jong-un ... must have turned to missile tests to seek ways out of this deadlock," South's President Park Geun-hye said in a TV interview on Sunday.

Meanwhile, inter-Korean relations have been soured by the suspension of operations at the jointly-run Kaesong Industrial Complex.

"It is very regrettable that the North denigrates our offer for talks ... and shifts blame for the suspension of the Kaesong complex to us," unification ministry spokesman Kim said Sunday, urging Pyongyang to come forward for talks as soon as possible.

AFP