North Korea said Saturday that a Britain-based senior diplomat who recently defected to South Korea is a "criminal."

Earlier this week, the South announced that Thae Yong-ho, who served as a minister at North Korea's embassy in London, and his family had arrived in South Korea.

In its first official response to the high-profile defection, the North accused the South of launching an "anti-DPRK (North Korea) smear campaign and confrontation."

"The Park Geun-hye group of traitors in South Korea carried out an operation to bring to South Korea a DPRK's diplomat who fled his mission in London with his family for fear of legal punishment for his crimes," the Korean Central News Agency said in an English dispatch monitored in Seoul.

The KCNA did not identify Thae by his name but claimed the fugitive "was instructed to return home in June last for questioning as regards the embezzlement of huge amount of state funds, leakage of state secrets for money and rape of a minor."

Thae, known as the No. 2 man at the North's embassy, has become one of the highest-level North Korean diplomats to desert the repressive regime, according to the Seoul government.

The KCNA also said Thae "deserved a legal punishment for his crimes."

The North also argued that it had already informed the London government of his extradition for investigation.

"However, the U.K handed over the fugitive and his family carrying no passports to the South Korean puppet forces, contrary to its duty to protect the foreign diplomats in its country, thereby besmirching its image as a law-governed state," the KCNA said.

Seoul's unification ministry said Thae defected because of his disillusionment with North Korea under leader Kim Jong-un and aspiration for freedom and democracy.

Concern for a better future for his children was also factored into his decision, it added.

North Korea previously also branded a former North Korean ambassador to Egypt who had fled in 1997 as criminal. (Yonhap)