UPDATE=

The Pentagon confirms North Korea conducted a missile launch in last 90 minutes which flew over Japan, and adds that the North Korea missile didn't threaten North America.

“We assess North Korea conducted a missile launch within the last 90 minutes. We can confirm that the missile launched by North Korea flew over Japan,” Pentagon says in statement.

U.S. says it’s still assessing launch; NORAD determined launch did not pose a threat to North America

“We are working closely with Pacific Command, Strategic Command and NORAD and will provide an update as soon as possible”

Update: Japan PM Abe, speaking to reporters in Tokyo after the launch, said North Korea appears to have fired a missile that flew over Japan. According to subsequent reports as many as three separate ballistic missiles may have been launched.

"It seems that DPRK missile passed over our airspace," Prime Minister Shinzo Abe said adding that the government was urgently collecting intelligence on the incident and doing everything to ensure the safety of its citizens.