North Korea fired two ballistic missiles on Wednesday. (AFP)

The United Nations Security Council will meet behind closed doors on Thursday to discuss North Korea's recent ballistic missiles tests, diplomats said.

Britain, France and Germany requested the discussion amid growing concern that Pyongyang is developing long-range weapons in violation of UN Security Council resolutions.

North Korea fired two ballistic missiles on Wednesday, Seoul said, days after a similar launch that the nuclear-armed North described as a warning to the South over planned joint military drills with the United States.

The North is banned from ballistic missile launches under UN Security Council resolutions but it was the second in less than a week, despite a meeting between leader Kim Jong Un and US President Donald Trump last month.

Pyongyang and Washington are engaged in a long-running diplomatic process over the North's nuclear and missile programs that has seen three high-profile encounters between their leaders in the space of a year.

They agreed to resume talks during their impromptu June encounter in the Demilitarized Zone that divides the peninsula, but that working-level dialogue has yet to begin.

"We'll be having consultations on North Korea on Thursday morning. We're going to discuss the latest missile launches that are violations of Security Council resolutions," a source told AFP.

A separate source said the discussions would form part of any other business, the last item on the agenda of a closed doors meeting being held to mark the first day of Poland's presidency of the Security Council.