That was the frightening scenario that confronted Canberra golfer Jones on Friday morning when North Korea fired a ballistic missile over the tournament he was playing at in Japan.

Warning sirens rang out around the northern island of Hokkaido where Jones was about to start his second round to defend his title at the ANA Open at the Sapporo Golf Club.

At first there was a frenzy of mobile phone alerts in the players' locker-room before someone translated to Jones the missile would fly overhead.

"Once it's in the air, I guess there's not much you can do about it to be honest," a frank Jones told Fairfax Media.

"You feel a bit helpless. But I never felt like I was threatened or we were threatened. Who knows what it's all about, but it is what it is.

"You can't go around being scared all the time."

Jones is part of the 120-strong field which was temporarily evacuated for a 40-minute delay before details emerged the missile flew east of Hokkaido and landed in the Pacific Ocean.

North Korea fired the missile before 7am from near Pyongyang, reaching an altitude of 770 kilometres, according to South Korea's military.

Jones has been playing on the Japan Tour for the past 15 years and said the missiles being launched wouldn't deter him from playing.

"While the tournaments are still being played, I'll still be here supporting the tour," Jones said.

"If things get more drastic, things might get postponed. But this is unchartered territory - no one knows where it's going or what's going to happen.

"But I'm happy to keep supporting the Tour. I sent a text message to [wife Adele] to say that we had a missile delay. I was just trying to get some updates in English, but they were slow to put things up.

"Everyone was huddled around TV sets to see what was going on and there was a translator trying to keep me up to date. But you're pretty much helpless.

"We've had storm delays, wind and rain ... but never missiles before."

Fellow Australian Matt Griffin told SEN Radio: "We woke this morning to an alert text message that said North Korea had launched a ballistic missile and then there was one a few minutes later that said that it's landed in the Pacific Ocean, so that was a fair relief.

"Over the last few months I guess tensions just gradually increased and you keep thinking or you hope that nothing will ever happen because it's so stupid if it does and you would think that North Korea would be obliterated if it does."

Jones was locked in a tie for ninth after the opening two rounds at the ANA Open, finishing his second round at five-under par after the missile delay.

Jones, who has won 17 titles in his professional career, is hoping his game clicks on the weekend to make a charge at back-to-back trophies.

"My game feels just a little bit off, but I felt in control [in the second round]. We've got 36 holes to go ... I just didn't want to make any mistakes," Jones said.

"I had plenty of chances for more birdies but I just wasn't quite sharp enough. With 36 holes to go, I can probably play a bit more aggressively over the weekend.

"We're getting to the business end of the season now. I feel fresh and ready to go."