If confirmed, they would be the latest in a series of killings, purges and dismissals carried out since North Korean leader Kim Jong Un took power in late 2011.
North Korea is a closed, authoritarian country with a state-controlled press that often makes it difficult for outsiders, and even North Korean citizens, to know what's happening in the government.
Rival South Korea, which runs several intelligence organizations mainly tasked with spying on North Korea, has a mixed record on reporting developments across the border. In May, a former North Korean military chief, who Seoul said had been executed, was found to be alive and holding several new senior-level posts.
But a South Korean official, speaking on condition of anonymity citing office rules, said Kim was executed by firing squad in July for unspecified anti-revolutionary and factional acts. The official said Kim first faced an investigation because of the way he was seated during a June meeting attended by Kim Jong Un.
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Kim Jong Un, believed to be his early 30s, is revered at the center of an intense cult of personality, with state TV occasionally showing aging senior officials kowtowing and kneeling down before him.
Last year, South Korea's spy agency said Kim had his defense chief executed with an anti-aircraft gun for complaining about him and sleeping during a meeting he had presided over.