SEOUL, South Korea — The chief of North Korea’s powerful secret police, long considered the right-hand man for the top leader, Kim Jong-un, has been dismissed on charges of corruption and abuse of power, the South Korean government said on Friday.

The firing of the chief, Gen. Kim Won-hong, as minister of state security highlights the turmoil that has engulfed the upper reaches of Mr. Kim’s government. The general is the latest in a series of high-ranking party and military officials Mr. Kim has fired, demoted or executed as he tried to consolidate his totalitarian power through what South Korean officials and North Korean defectors have called a “reign of terror.”

General Kim was fired in mid-January after he was demoted to a one-star general from a four-star one, said Jeong Joon-hee, a spokesman for the South’s Unification Ministry.

The general’s surprise downfall was the latest indication that even top lieutenants are at risk as Mr. Kim has rival agencies monitor one another to detect and punish any sign of disrespect or disloyalty. Until his dismissal, General Kim had been Mr. Kim’s chief henchman in purging potential enemies.