These photos from Monday, show Seoul (right) and its adjacent city of Incheon that the country claimed were taken from a "test-piece satellite" that it fired the previous day. (KCNA)

The sister of North Korean leader Kim Jong-un issued a statement Tuesday criticizing those who question the secretive regime's assertion of having made significant progress in its satellite and long-range missile development.

Kim Yo-jong, vice department director of the Central Committee of the Workers' Party of Korea, took issue with a view among experts in the outside world, including those in South Korea, that low-resolution, black-and-white images of Seoul and Incheon, released by Pyongyang the previous day, are too crude to be satellite photos.

The North claimed the launch of rockets as part of its military reconnaissance satellite project and made public those two photos, presumed to be taken from a mock satellite.

Some experts here soon said that the quality of the imagery is too poor.

Kim said it's "inappropriate and hasty" to assess the North's satellite development capabilities and relevant preparations with the two photos alone.

She also condemned those who question whether the North has mastered the atmospheric re-entry technology for its intercontinental ballistic missile. (Yonhap)