A North Korean defector prepares to release balloons bearing leaflets condemning North Korean leader Kim Jong Il and his son Kim Jong Un during an anti-North Korea demonstration at the Imjingak Pavilion, near the border village of Panmunjom in South Korea on Dec. 21, 2011. (Wally Santana/AP)

SEOUL — With tighter border security and harsher punishments for those who cross into China, North Korea has forced a swift and drastic drop-off in defections this year, according to aid groups and South Korean officials.

The crackdown, they say, coincides with the rise of new leader Kim Jong Eun, and suggests that his authoritarian police state is not only worried about people leaving the country, but also strong enough to stop them.

As many as 20,000 additional soldiers have been dispatched to the Chinese border, according to Seoul’s Open Radio for North Korea, which has a network of contacts in the North. Those guards, threatened with punishment of their own, have become less willing to take bribes from would-be defectors, other aid groups say.

As a result, outside experts say, the number of North Koreans entering the South after a circuitous journey through China is plummeting.

Last year, 2,706 North Koreans came to the South. During the first half of this year, there have been only 751 — a 42 percent decline compared with the same period a year earlier.

The unprecedented drop off reverses a 15-year trend. The downturn is especially jarring because it challenges an underlying assumption held by many analysts in the South that the North would face an ever-mounting problem keeping people within its borders. Indeed, after the North’s famine in the mid-1990s, the number of defectors arriving in the South rose exponentially — from fewer than 100 in 1997 to more than 1,000 in 2002 to nearly 3,000 in the past few years, according to South Korea’s Ministry of Unification.

‘Very closely watched’

“The border with China used to be essentially unguarded,” said Andrei Lankov, a North Korea expert at Seoul’s Kookmin University, who speaks frequently with recent defectors. “It is now very closely watched.”

Lankov predicted that the drop-off could be long-lasting because “the North has now invested all this money in border control,” and it has seen that it works. “Now it’s very easy to maintain it.”

North Koreans who attempt to enter China and travel to the South have long been subjected to punishment, often sentencing in one of the North’s detention camps. But after Kim Jong Il’s death this past December, according to information from recent defectors, government authorities visited towns and described a more severe policy: No longer would the North grant leniency to those who say they are simply visiting China to get money or medicine. During the 100-day mourning period for the Dear Leader, not only would captured escapees be punished — so, too, would their families.

Evidence suggests that North Korea has not loosened its border control after the mourning period ended, because there’s been little change in month-to-month arrivals in the South. Between January and March, 366 came to the South. Between April and June, 385 came.

The South Korean government attributes the relatively low numbers to “stronger control in North Korea after the death of Kim Jong Il,” according to an official at the Ministry of Unification who requested anonymity, citing the sensitivity of speaking about inner-workers in the North. “However, we still need to closely monitor the situation before making a judgment if the current situation will continue.”

Cellphone punishment

Accounts vary about other specific methods used to clamp down on defectors, and there is no way to independently confirm conditions in the secretive North, which limits foreign visitors and usually prevents them from seeing its rural, impoverished countryside. But one South Korea-based aid organization reported in April that anyone caught with a Chinese-made cellphone — frequently used for arranging defections — would be sentenced to three years in a “re-education center.”

Border security slows North Korea defections (By The Washington Post/South Korea’s Ministry of Unification)

“At every lecture, security officers make sure to emphasize the threat that no one will be forgiven for betraying their country,” the aid organization, Good Friends, wrote in its weekly newsletter.

Taken together, the measures make it costlier and riskier for those who want to leave. To bribe a border guard, one now needs as much as $6,000, said Son Jung-hun, who runs a Seoul-based organization that helps defectors escape and move through China. Several years ago, Son said, defectors could do the trick with $1,000.

“Guards don’t want to take a risk unless they’re getting a lot of money,” said Son, whose organization used to help 10 escapees per month. This year, he said, that number has fallen to one, or sometimes none.

When defectors do arrive in South Korea, they are sent to Hanawon, a resettlement center that Seoul created in 1999 to help with the adjustment from dictatorship to democracy. There, almost all defectors are interviewed by a staff member from the Database Center for North Korean Human Rights, a Seoul-based group that collects information on conditions in the North.

The group’s president, Yoon Yeo-sang, said recent defectors appear increasingly reluctant to send for their families. For years, defectors have swelled their ranks by settling in the South, finding jobs and building their savings, and then sending that money to their relatives in the North — providing cash that can help them escape. But this cycle, Yoon said, is now on hold. Defectors are sending less money, because fewer want their relatives to be tempted to flee.

“Family members don’t want loved ones [still in the North] to risk their lives at this time,” Yoon said.

Yoonjung Seo contributed to this report.