The isolated North Korea on Monday said the launch on the previous day was aimed at verifying its capability to carry a "large scale heavy nuclear warhead".
Amid condemnation in Seoul, Tokyo and Washington, a jubilant leader Kim Jong Un promised more nuclear and missile tests and warned that North Korean weapons could strike the USA mainland and Pacific holdings.
Pyongyang's propaganda must be considered with caution, but if confirmed, the claim marks another big step forward in the country's escalating efforts to field a nuclear-tipped missile capable of reaching the USA mainland. North Korea's push to boost its weapons programme also makes it one of the Trump administration's most urgent foreign policy worries.
North Korea has never launched a missile that can fly across the Pacific.
Japanese officials say the missile flew for about 30 minutes, traveling about 800 kilometers (500 miles) and reaching an altitude of 2,000 kilometers (1,240 miles).
North Korea has been testing missiles for weeks, and the status of their nuclear weapons development program has been a source of questions and concern for years.
"This is the longest-range missile North Korea has ever tested", Jeffrey Lewis of the Middlebury Institute of International Studies told AFP.
But he slammed the latest missile test as a "reckless provocation" and said dialogue would be possible "only if the North changes its attitude".
"The members of the Security Council strongly condemned the most recent ballistic missile launches conducted by the Democratic People's Republic of Korea on 28 April and 13 May 2017", the council members said in a press release for the media.
The U.S. ambassador to the United Nations, Nikki Haley, said on ABC television that the United States has been working well with China, Pyongyang's closest ally, and raised the possibility of new sanctions against North Korea, including on oil imports.
The 38 North analysis points out that the distance flown by the missile means it could strike a USA military base at Guam.
That signalled a new phase in applying sanctions that curb exports of coal from North Korea, impose severe restrictions on banking and ban sales of luxury goods and equipment that could be of use to the military. It said that with this missile, "the USA mainland and Pacific operation region are in the [Democratic People's Republic of Korea's] sighting range for strike". He also warned North Korea not to test his resolve.
Moon, South Korea's first liberal leader in almost a decade, said as he took his oath of office last week that he'd be willing to visit North Korea if the circumstances were right.
Preliminary assessment by USA authorities indicates that North Korea launched a liquid-fuel single-stage KN-17 missile, NBC News reported citing two military officials.
North Korea has been a flagrant menace for far too long.
Trump also said earlier this month he would be "honored" to meet with Kim under appropriate circumstances, although the White House quickly walked that back to stress the current conditions were not right.
On Monday, Russian President Vladimir Putin condemned the launch as "counterproductive, damaging, dangerous". In a show of force, the United States sent an aircraft carrier strike group, led by the USS Carl Vinson, to waters off the Korean peninsula to conduct drills with South Korea and Japan.