SEOUL, South Korea — The news yesterday that Kim Jong Un purged his uncle and de facto number two leader of North Korea, Jang Sung Taek, has all the trappings you’d expect from a mysterious and ruthless dictatorship.

On Tuesday, the National Intelligence Service (NIS), South Korea’s spy agency, made the announcement before a National Assembly meeting, citing the disappearance of Jang from state media for weeks and the possible public execution of close assistants on corruption charges.

But many South Koreans — along with the global line-up of North Korea experts — quickly expressed skepticism.

The allegations may turn out to be true, and more evidence will likely emerge in the coming weeks. But the NIS has a less-than-stellar track record when it comes to exposing the inner workings of its brother enemy, North Korea.

In Seoul, opposition lawmakers aren’t afraid to pillory the all-powerful body, which is sometimes called in jest the “Neighborhood Intelligence Service.” In addition to its shortcomings on North Korea, its agents have a history of getting caught red-handed in shady operations. They’re even alleged to play politics with national security.

Earlier this year, prosecutors brought forward evidence of a massive online propaganda campaign to influence the December 2012 presidential election on behalf of the conservative victor. Undercover agents allegedly posted some 1.2 million tweets vilifying the left-wing opposition candidate as a North Korea sympathizer, or praising the conservative candidate, Park Geun-hye. The spy chief, Won Sei-hoon, was indicted on claims that he personally oversaw the operation, becoming the eighth NIS leader to be investigated in the past two decades.

In other words, many South Koreans harbor a deep distrust of the agency.

Here are four major intelligence failures that have helped establish the agency’s bumbling reputation here in Seoul — all the more reason not to take its claims at face value.

Kim Jong Il’s death

On Dec. 17, 2011, Kim Jong Il, the father of the current dictator, reportedly collapsed and died of a heart attack on his personal train. It was terrible news for the regime, which went to great lengths to keep Kim’s demise secret for two days. A weeping television broadcaster made the official announcement the following Monday.

Hours before the announcement, a few North Korean defectors in the South knew something was up, alerting journalists to the fact that television announcements normally didn’t happen on Mondays and that state media aired videos all morning about Kim Jong Il.

It was a development with huge national security implications. But the NIS (and other intelligence bodies), which kept tabs on the hermit kingdom through a network of sources inside the country, were blindsided. In Seoul, opposition lawmakers called for the resignation of top spies. One prominent politician proclaimed the floundering agency was a “laughing stock.”

To be fair, the NIS was not alone. The CIA and MI6 didn’t know Kim Jong Il had met his demise in the days leading up to the television announcement, either.

Naval attack and island shelling

In 2010, Seoul accused the North of torpedoing and sinking a naval corvette, the Cheonan, killing 46 servicemen. The provocation was the most serious in a decade, but came with no foresight from the NIS.

Making matters worse, eight months later North Korea flung artillery shells at a tiny South Korean island off the North’s west coast, killing four more people. In the press, the agency came under fire once again for a perceived failure.

The spy body tried to deflect the blame at the presidential Blue House, claiming that it warned of the second attack months earlier. The president’s office responded that the prediction was so vague and amateur that any casual observer could make it.

As if that’s not enough, the NIS came forward with a bold and brilliant prediction. “There is a high possibility that the North will make another attack,” then-director Won Sei-hoon told reporters. That prediction, thankfully, has yet to come true.

Busted breaking into a hotel room

In February 2011, a high-level Indonesian delegation visited Seoul, looking into the purchase of South Korean trainer jets. When the group of 50 military officers and policymakers left their hotel, two men and a woman broke into one room, allegedly agents from the NIS, police later said.

A delegate returned and caught the woman in his room; later reports suggested she was combing a laptop for information on Indonesia’s negotiation strategy. The NIS denied any connection, but other officials publicly admitted that the agency was the culprit.

The press also revealed, based on government sources, that the NIS was operating a permanent “safe house” in the Lotte Hotel in central Seoul, essentially a forward base for keeping tabs on foreign VIPs. So much for that secret.

Spying on the United Nations?

Thanks to harsh interpretation of its criminal defamation laws, South Korea doesn’t have a great track record on free speech — in spite of its status as a developed democracy. This trend became particularly heinous under the previous president, Lee Myung-bak.

In 2010, the United Nations special rapporteur for free expression, Frank La Rue, visited South Korea on a fact-finding mission at the invitation of the government. But upon his arrival, he immediately felt he was being followed. At a meeting with the foreign ministry, he presented photos of a mysterious figure filming him from another car.

The NIS and national police denied the vehicle belonged to the spy agency. The Korean press opined otherwise, igniting yet another embarrassing scan