North Korea fired two short-range missiles into the sea on Thursday, South Korea’s joint chiefs of staff has said, after warnings from Pyongyang over military exercises between Washington and Seoul next month.

The North has warned the war games could affect the planned resumption of denuclearisation talks between Washington and Pyongyang.

The North fired one missile at 5.34am and a second at 5.57am, from Wonsan areas into the East Sea, and they flew about 430km (267 miles), Seoul’s joint chiefs of staff said in a statement. “Our military is closely monitoring the situation in case of additional launches and maintaining a readiness posture.”

Japan’s Kyodo News said, citing an unnamed government source, that the missiles did not reach Japan’s exclusive economic zone and had no impact on Japan’s national security.

In Washington a US official, speaking on condition of anonymity, said: “I can confirm that it was ... short-range.”

Pyongyang last fired short-range missiles on 9 May, a move US president Donald Trump called “very standard stuff” that, he said, had not affected his relationship with the North’s leader Kim Jong-un.

Kim and Trump agreed to a resumption of dialogue at an impromptu meeting on 30 June they held in the demilitarized zone that divides the two Koreas.

Following that meeting, US secretary of state Mike Pompeo said working-level talks would probably start in mid-July. But last week, North Korea issued a warning over the military drills, which have been held for years and were scaled down to ease tensions with the nuclear-armed state.

The North condemned the exercises as “blatant pressure” and a “violation of the spirit” of the joint statement Trump and Kim signed at their first summit in Singapore last year.

The North even hinted it could reconsider its moratorium on nuclear testing because of the drills, although the US State Department had remained upbeat over commitments made by Kim and Trump during the DMZ encounter and at a February summit in Vietnam.

At their first summit in Singapore in June 2018 the two adopted a vaguely worded statement on “complete denuclearisation of the Korean peninsula” and agreed to “establish new US-DPRK relations”.

But the failure to reach an agreement over relief from US sanctions, and what the North was willing to give in return, led to the collapse of the leaders’ second summit in Hanoi.

Tensions rose in May, during the standstill in negotiations between Trump and Kim, when North Korea fired short-range missiles for the first time since November 2017.

“I don’t consider that a breach of trust at all. And, you know, at some point I may. But at this point no,” Trump said in an interview with Politico at the time.

Asked on Tuesday whether any meetings were scheduled with the North, Trump said: “No, we just have a very good relationship. And probably they would like to meet and we’ll see what happens.”

“There was a little correspondence recently, very positive correspondence with North Korea.”

He said there had been “no nuclear testing, there’s no missile testing, there’s no nothing.”