SEOUL - Staff at embassies in Democratic People's Republic of Korea appeared to be remaining in place on Saturday despite an appeal by authorities in Pyongyang for diplomats to consider leaving because of heightened tension after weeks of bellicose exchanges.

DPRK authorities told diplomatic missions they could not guarantee their safety from next Wednesday - after declaring that conflict was inevitable amid joint US-Republic of Korea military exercises due to last until the end of the month.

Whatever the atmosphere in Pyongyang, the rain-soaked ROK capital, Seoul, was calm. Traffic moved normally through the city centre, busy with Saturday shoppers.

ROK's Yonhap news agency quoted a government official as saying diplomats were disregarding the suggestion they might leave the country.

"We don't believe there's any foreign mission about to leave Pyongyang," the unidentified official was quoted as saying. "Most foreign governments view the DPRK's message as a way of ratcheting up tension on the Korean peninsula."

DPRK has been angry since new UN sanctions were imposed following its third nuclear weapons test in February. Its rage has apparently been compounded by joint US-ROK military exercises that began on March 1.

China's Xinhua news agency on Friday had quoted the DPRK Foreign Ministry as saying the issue was no longer whether but when a war would break out.

Most countries saw the appeal to the missions as little more than strident rhetoric after weeks of threatening to launch a nuclear strike on the United States and declarations of war against the South.

But Russia said it was "seriously studying" the request.

A ROK government official expressed bewilderment.

"It's hard to define what is its real intention," said the official, who asked not to be identified. "But it might have intensified these threats to strengthen the regime internally or to respond to the international community."

The United Nations said its humanitarian workers remained active across DPRK. Secretary General Ban Ki-Moon, however, remained "deeply concerned" about tensions, heightened since the imposition of UN sanctions against the DPRK for its third nuclear arms test in February.

Chinese Foreign Minister Wang Yi repeated Beijing's calls for dialogue to resolve the tensions in a phone call with Ban.

"We oppose provocative words and actions from any party in the region and do not allow troublemaking on China's doorstep," a statement on the ministry's website said, citing Wang.

The appeal to diplomats followed news reports in the ROK that DPRK, under its 30-year-old leader Kim Jong-un, had moved two medium-range missiles to a location on its east coast. That prompted the White House to say that Washington would "not be surprised" if the DPRK staged another missile test.

DPRK has always condemned the exercises held by US forces and their ROK allies. But its comments have been especially vitriolic this year as the United States dispatched B-2 bombers from its home bases to stage mock runs.