SEOUL — A colonel belonging to North Korea’s spy agency recently defected to South Korea, the South announced Monday. He is one of the highest-ranking North Korean military officers known to have defected to South Korea in recent decades.

The Defense and Unification Ministries of South Korea would only confirm that a colonel from the North’s General Bureau of Reconnaissance had recently defected, declining to provide further details.

The South Korean news agency Yonhap, which earlier reported the officer’s defection, said he arrived in South Korea last year. A few South Korean news outlets also reported Monday that a North Korean diplomat stationed in an African country defected to the South last May. The government confirmed that defection as well.

The revelations came three days after South Korea confirmed Friday that 13 North Koreans working for a North Korean government-run restaurant abroad defected to the South a day earlier.

Some South Korean news outlets quoted unidentified government sources as saying that the colonel had been involved in running spy operations against South Korea while working in the North, indicating that his defection could have handed a potential trove of intelligence to the South Korean authorities.

It has been rare for South Korean officials to publicly confirm the defections of North Koreans, especially those of high rank. Even when they have, they usually waited until after the government had thoroughly debriefed the defectors and was reasonably sure that announcing their defections would not jeopardize family members left in the North.

Opposition political parties accused the conservative government of President Park ­Geun Hye of advertising the high-profile defections in recent days to help attract votes in parliamentary elections set for Wednesday.

The government denied that the announcements were politically motivated. Jeong Joon Hee, a spokesman for the Unification Ministry, said the defections of 13 North Koreans last week were significant enough to be announced because they came while the North was being punished with UN sanctions.