North Korea is unlikely to stand idle in the wake of the high-profile defection of the country's deputy ambassador to London, Thae Yong Ho, South Korean officials cautioned.

An official from South Korea's Unification Ministry told Sky News the recent defection had put North Korean leader Kim Jong-Un in "a very difficult situation". And that the pariah state may attempt to kill other defectors.

The unnamed official said that given Kim's character the situation was now "very dangerous".

"It is highly likely that North Korea will make various attempts to prevent further defections and unrest among its people," he added, explaining that assassination attempts on those who had already defected and were living in South Korea were also likely.

Hwang Jang-Yop, a former tutor to the previous leader Kim Jong-Il, who defected to South Korea in 1997 was the target of various unsuccessful assassination attempts. However, Hwang died of natural causes in 2010.

Thae is the highest ranking diplomatic official to ever defect to South Korea. In response to his defection, along with his family, for whom he said he wished a better life, North Korea has described him as "human scum".

North Korea has described Thae, who fled North Korea's control with his family, as "human scum" who fled because he had embezzled state funds, raped a child and spied for the South.

"He thus revealed himself as human scum bereft of elementary sense of moral obligation and conscience," The North Korean news Agency KCNA was quoted as saying.

Prior to his defection, Thae had lived in the UK for 10 years before disappearing from his home in west London a few weeks ago. His defection comes amid a string of similar North Korean defections, including 12 waitresses who worked at a restaurant in China and defected to South Korea.

Several diplomats have previously defected from North Korea to the South over the last two years.

While the overall number of defectors has declined under Kim Jong-Un, there have more political defections since he took over from his father in 2011.