SEOUL, South Korea — Officials from North Korea’s secret police and Foreign Ministry were involved in the killing of the estranged half brother of the country’s leader, South Korean intelligence officials told lawmakers on Monday.

Ever since Kim Jong-nam, the eldest brother of the North Korean leader, Kim Jong-un, was first reported assassinated, the South Korean government has held the North responsible. On Monday, the National Intelligence Service in Seoul provided more details of what it described as state-sponsored terrorism, saying that four of the eight North Koreans identified as suspects by the Malaysian authorities were agents from North Korea’s Ministry of State Security, the country’s secret police.

Speaking on Monday in a closed-door parliamentary hearing, Lee Byung-ho, the director of the National Intelligence Service, said that two other suspects worked for the North Korean Ministry of Foreign Affairs. The remaining two were affiliated with Air Koryo, the North’s state-run airline company, and Singwang Economics and Trading General Corporation, Mr. Lee said, according to two lawmakers who attended the briefing. Singwang is among North Korean companies facing United Nations sanctions.

The Malaysian authorities have said that Mr. Kim was killed by an extremely toxic nerve agent known as VX. They said that the North Koreans had hired and trained two women, one from Indonesia, the other from Vietnam, to attack Mr. Kim at Kuala Lumpur International Airport. The women smeared his face with the chemical while he was waiting to check in for a flight to Macau, where he and his family had a home, they said.