SEOUL (REUTERS) - North Korea fired two mid-range ballistic missiles into the sea off its east coast and towards Japan early on Wednesday, South Korea's military said as the leaders of South Korea, Japan and the United States (US) discussed North Korea's arms programmes.

The missiles, which appeared to be Rodong class, were launched from an area north of Pyongyang and flew about 650km before dropping into the water, said an official at South Korea's office of the Joint Chiefs of Staff, who asked not to be named.

The North likely launched the missiles to drop short of its maximum range, which is believed to be more than 1,000km and enough to hit much of Japan, "mindful of neighbouring countries' reaction", the official said, without elaborating.

Wednesday's launch came on the day Japanese Prime Minister Shinzo Abe met South Korean President Park Geun Hye and US President Barack Obama.

Mr Obama, speaking after meeting both leaders on the sidelines of a nuclear security summit in The Hague, said the three countries had presented a united front against the threat posed by North Korea's arms programmes.

The launch followed a series of short-range missiles fired over the past two months, and was seen as an act of defiance toward the annual South Korean-US joint military drills that are currently underway.

The North's ambassador to the United Nations in Geneva So Se Pyong said on Tuesday the country was conducting routine military exercises, when asked about the timing of the missiles coinciding with joint US-South Korea military drills.

Pyongyang routinely denounces annual US and South Korean joint military exercises as preparation for war.

The North was angered in February when a nuclear-capable US B-52 bomber made a sortie over South Korea, though the flight did not trigger the sharp escalation of military tension that was seen a year ago.