Yet apparently no one, including South Korean intelligence services, was aware that North Korean leader Kim Jong-il had died early on Saturday - until his passing was tearfully announced on state television on Monday.

That medium itself appears antiquated in South Korea, frequently cited as the most wired country on the planet, where news is increasingly delivered and dissected via smartphone and social networking services.

A night-time image of the Korean peninsula taken by an intelligence satellite in 2002 shows North Korea as a pool of darkness, in stark contrast to the blazing sea of light that is its prosperous southern neighbor on the other side of the world's most heavily militarized border.

A decade later, little has changed.

Kim's death appears to have been kept a close secret within a tight coterie at the top of the reclusive North. There was no stream of Facebook or Twitter posts from the Internet-deprived country to spread the news as with the "Arab Spring."

South Korea's Internet users, accustomed to a near-instantaneous flow of information, were nearly as struck by the delay in the announcement as the news itself.

"The depth of information that South Korean intelligence sources have (on the North) is shallower than that of Twitter," posted user Links_Arc, referring to the popular microblogging service. "It's very regrettable that the government only found out about Kim's death two days later."

"The current government's hostile policy toward the North has resulted in a shutdown of communication channels with the North, and China raising its influence over Pyongyang," chimed in user EuiQKIM.

FEW PHONES, BUT GROWING

The North Korean regime's chokehold on information is made relatively easy by the country's limited communications infrastructure, making an Arab Spring-type scenario almost impossible, analysts say.

According to International Telecommunications Union data, North Korea had fewer than two mobile phone subscriptions per 100 inhabitants last year. South Korea had 105.

While 83 percent of South Koreans have regular Internet access, it remains unavailable in the North outside a handful of government ministries, hotels and diplomatic enclaves in Pyongyang.

North Koreans with mobile phone and Internet access are "pro-government, pro-regime. They have nothing to gain from trying to organize an uprising. So, in that sense, it's hardly a useful anti-regime tool," said Cho Min, an expert at the Korea Institute for National Unification.

South Korean bloggers' responses to Kim's death illustrated the ease with which potentially seditious messages can now be broadcast to a mass audience, something North Korean authorities have taken pains to prohibit.

Many Twitter users posted messages of sympathy and even praise for Kim, despite rhetoric perceived as pro-North possibly running foul South Korea's national security regulations.

"I pray for the bliss of the deceased Kim Jong-il," wrote user "helliumgas."

Agencies with contacts in Pyongyang said Kim's death was likely to prompt the authorities to tighten their grip on communications even further.

"We're expecting some form of lockdown on communications and travel in the immediate period as North Korean authorities move to stabilize the situation and prepare for mourning," said Geoffrey See, managing director at Chosun Exchange, a Singapore-based non-profit group that promotes academic exchanges with North Korea.

There are some signs, however, that the regime's control on communications may be slipping. Mobiles are now increasingly commonplace among Pyongyang residents, and not just among the regime elite, said Simon Cockerell of Beijing-based Koryo Tours, which operates trips to North Korea.

In the last couple of years, mobile phone use has "just exploded," he said, with people often using mid-range, China-made handsets to trade SMS messages, play games and browse weather reports.

North Korea is this year expected to register the 1 millionth user of its new 3G mobile network, built in partnership with Egypt's Orascom.

The North's mobile communications industry "has crossed the Rubicon, and the government can no longer roll it back without paying a severe political price," the Nautilus Institute for Security and Sustainability said in a report last month.

(Additional Reporting by Jack Kim, Miyoung Kim and Iktae Park; Editing by Ian Geoghegan)

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