TOKYO -- North Korea's successful intercontinental ballistic missile (ICBM) launch is now music to its leader's ears -- quite literally.

Kim Jong Un was feted at a concert replete with pop music and thunderous applause marking last week's successful launch of his country's first intercontinental ballistic missile.

But as Kim was lauded, South Korean officials cast new doubt on one of the key claims made by the North Korea following its successful test of the long-distance rocket.

While U.S. officials have confirmed the missile fired was an ICBM, there has been no proof of the North's claim that the test also demonstrated the ability to get a missile -- and more importantly its deadly payload -- back into the Earth's atmosphere intact. This technical ability, known as "re-entry," has been a key hurdle for North Korea's long-range missile program.

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On Tuesday, a member of the South Korean legislature's intelligence committee said his country did not believe the July 4 test had, in fact, demonstrated a re-entry capability.

Parliamentarian Yi Wan-young said during a televised news briefing that South Korea's National Intelligence Service had not been able to confirm that the rocket re-entered the atmosphere.

"Considering how North Korea does not have any testing facilities (for re entry technology), the agency believes (North Korea) has not yet secured that technology," he said.

In Pyongyang, however, the mood celebratory. Among the numbers performed at the weekend concert in honor of Kim and his missile, were "Song of Hwasong Rocket" and "Make Others Envy Us," the North's official Korean Central News Agency reported.

Leading the bill at the concert was the Moranbong Band, an all-female ensemble that was hand-picked by Kim and serves as something of the "soft" face of his regime.

Pyongyang has been the scene of a slew of special events to mark the July 4 launch of Hwasong-14, which is believed to be capable of reaching most of Alaska and possibly farther.

The launch is being treated as a major national milestone in North Korea, with the government and media touting it as a technological breakthrough few other nations have achieved.

The concert, which took place on Sunday before a packed crowd, many in uniform, also featured dancing.

Clips of the concert shown on North Korean television on Monday showed the crowd repeatedly cheering and applauding for Kim.

Along with the Moranbong Band, the concert had North Korea's other top headliners -- a similar pop ensemble called the Chongbong Band, the uniformed State Merited Chorus and the Wangjaesan Art Troupe.