SEOUL: South Korea's spy agency said Friday that Pyongyang was plotting "terrorist" attacks targeting Seoul's officials and citizens overseas, with the foreign ministry raising the alert level for diplomatic missions in five countries.

The National Intelligence Service said it had recently "detected numerous signs that North Korea is preparing for terrorist attacks against our embassy staff or citizens in various countries, (such as) China, Southeast Asia, and the Middle East".

"North Korea has dispatched agents to these countries to expand surveillance of the South Korean embassies and is also engaging in specific activities such as searching for South Korean citizens as potential terrorist targets," it said in a statement.

The spy agency said it appeared linked to a wave of defections by elite North Koreans who were trapped overseas during the pandemic and are now seeking to avoid returning home after Pyongyang eased strict border controls.

Pyongyang treats defections as a serious crime and is believed to hand harsh punishments to transgressors, their families, and even people tangentially linked to the incident.

North Korean embassy officials may be submitting false reports blaming "external factors" for voluntary defections by their colleagues, in a bid to evade punishment, the NIS said.

As a result, the North may be "plotting retaliation" against South Korean embassy staff on such pretenses, NIS added.

On Thursday, South Korea's foreign ministry said it had raised its anti-terrorism alert status for five of its diplomatic missions -- embassies in Cambodia, Laos, Vietnam as well as its consulates in Russian port city Vladivostok and the Chinese city of Shenyang.

Both Seoul and Pyongyang have embassies or consulates in all five locations.

North Korea has diplomatic ties with more than 150 countries, according to Seoul's Unification Ministry, but the number of missions it maintains overseas has been shrinking since the 1990s due to financial constraints.

Late last year, North Korea shuttered a handful of embassies including in key African allies Angola and Uganda and places from Spain to Hong Kong, in what Seoul claimed was a sign of the country's dire economic straits, but Pyongyang defended as streamlining.

According to Seoul's unification ministry, 196 North Korean defectors arrived in the South last year, with around 10 of them being from Pyongyang's elite class, such as diplomats and possibly their children.

This marked the highest number of defections by North Korean elites to the South since 2017, according to Seoul.

This year, Pyongyang's leader Kim Jong Un has declared Seoul his country's "principal enemy", jettisoned agencies dedicated to reunification and outreach, and threatened war over "even 0.001 mm" of territorial infringement.