Seoul (South Korea) (AFP) - North Korea's Kim Jong-Un ordered the execution of 15 senior officials this year, including several who complained about the young leader's policies, South Korea's intelligence agency said Wednesday.

Those executed included two vice minister-level officials, the Yonhap news agency reported, citing legislators who attended a briefing by the National Intelligence Service (NIS).

Both were punished for opposing or complaining about Kim's directives, the legislators said, adding a vice forestry minister was executed for complaining about Kim's forestation plan.

As well as the 15 senior officials, the NIS said four members of North Korea's Unhasu Orchestra, with which Kim's wife, Ri Sol-Ju, had once been a singer, were executed in March.

The NIS said they were executed by firing squad on charges of spying.

In 2013, Japanese and South Korean media reported that a number of members of the orchestra had been executed for violating pornography laws in a bid by Kim to protect his wife's reputation.

The Kim dynasty has ruled reclusive and impoverished North Korea for more than six decades with an iron fist and a pervasive personality cult.

The NIS suggested Kim Jong-Un was following the well-trodden path of his father and grandfather in using regular purges and executions to ensure discipline and loyalty.

Kim had his uncle and one-time political mentor Jang Song-Thaek executed in late 2013 on an array of charges, including treason and corruption.

Jang had played a key role in cementing the leadership of the inexperienced Kim, who took over after the death of his father and long-time ruler Kim Jong-Il in December 2011.

But analysts said Jang's growing political power and intervention in lucrative trade deals was resented by his young nephew.

The NIS said Kim Jong-Un's younger sister, Kim Yo-Jong, who has risen swiftly through the leadership ranks, appeared to have married her college classmate and was expecting a baby next month.

Analysts say Kim Yo-Jong, who once studied with her brother in Switzerland, wields increasing influence as the head of a propaganda unit in charge of her brother's official visits.

She has regularly accompanied her brother on his "field guidance" trips since she was named as part of the powerful National Defence Commission in 2013 and granted a senior party title late last year.