Asked whether there was any credence to American, Japanese and Chinese assertions -- or whether the launch was meant to satisfy military or scientific purposes, or to honor Kim -- the source sent a written response to CNN.
It was the "best possible gift for Generalissimo Kim Jong Il on his 75th birthday," said the source, whom CNN is not naming. Kim died in 2011
The Day of the Shining Star, a two-day celebration of Kim's birth, is set to begin Thursday. In addition to concerts, fireworks and military displays, North Koreans will flock to the Kumsusan Palace of the Sun, where the former leader and his father were laid to rest.
The North Korean response also said the rocket, which began as a submarine-launched ballistic missile, took six months to build and that it was fired with a steep trajectory to ensure the safety of neighboring nations.
It was not clear if the source was refuting speculation that the launch, confirmed Sunday, was meant to coincide with a meeting between Japanese Prime Minister Shinzo Abe and President Donald Trump
in the United States.
Japanese Chief Cabinet Secretary Yoshihide Suga said the launch was "a clear provocation to Japan and the region." Tokyo lodged protests against North Korea via its embassy in Beijing, he said.
The North Korean source's statement also didn't address Chinese Foreign Ministry spokesman Geng Shuang's explanation Monday that "the root cause" of the launch "is the conflicts between North Korea and the United States, as well as between North and South Korea."
According to state-run Korean Central News Agency, North Korean leader Kim Jong Un personally ordered the launch of the previously unpublicized medium long-range Pukguksong-2 ballistic missile Sunday.
The news agency described the missile as a "Korean style new type strategic weapon system." It is capable of carrying a nuclear warhead and "evading interception," KCNA reported.
A US official said the missile traveled 500 kilometers (310 miles) before landing in the Sea of Japan, also known as the East Sea. It was launched from North Pyongan province, the official said.
Missile had message?
At least one expert told CNN he believes the data gathered from launching this type of missile would be useful in the development of an intercontinental ballistic missile program.
"Any experience that a launch crew and scientist and technicians can gather from live firing of ballistic missiles is applicable to an ICBM program," said senior analyst Joseph Bermudez of 38 North, a website dedicated to North Korea analysis. "In addition, any experience that the military can gain from an operational test of a ballistic missile helps it develop experience, skills that are applicable to an ICBM."
He added, "In order to develop successful ballistic missiles, you have to launch them."
Besides bolstering ICBM expertise, the launch sent a message domestically that Kim Jong Un has the reins of North Korea firmly in hand, and that the daily sacrifices by the North Korean populous were necessary to counter perceived threats posed by the United States.
"This is the reason why you are sacrificing. This is the reason why you don't have the highest quality of food, you have to work extra hours," Bermudez said, summarizing the underlying message meant for the North Korean people.
North Korea is prohibited from carrying out ballistic missile launches under UN Security Council resolutions aimed at curbing the country's development of nuclear weapons.
North Korea conducted an unprecedented number of missile tests in 2016 and a satellite launch that experts said was a sign it has cleared significant hurdles toward ICBM technology. But until Sunday, it hadn't tested a ballistic missile since October 20.
At the request of the United States, South Korea and Japan, the Security Council condemned the launch during an emergency session Monday. More notable, however, was what many saw as the US ambassador's veiled shot at China.
, the US ambassador to the United Nations, said it was "time to hold North Korea accountable, not with our words, but with our actions," but she took another step in denouncing those who help the regime.
"We call on all members of the Security Council to use every available resource to make it clear to the North Korean regime, and its enablers, that these launches are unacceptable," she wrote in a statement.
China concurred with the Monday statement
calling the launch a violation of North Korea's obligations under Security Council resolutions. But Beijing, which is North Korea's primary ally and trading partner, has resisted more drastic attempts to toughen sanctions, including efforts to implement an oil embargo.
The council has slapped six rounds of economic and military sanctions on North Korea, but none has pressured Kim Jong Un to halt ballistic missile launches and nuclear tests.