Korea's top 30 business groups reduced the number of their executives by about 500 over the past year due mainly to downsizing and business restructuring moves, data showed Wednesday.

The total number of senior executives at the 30 largest conglomerates was 9,632 as of May 16, down 484, or 4.8 percent, from a year ago, according to the data compiled by corporate researcher CEO Score.

Leading conglomerate Samsung Group shed the largest number of executives at 374 in the process of selling its defense unit to Hanwha and chemical unit to Lotte.

Doosan Group, a heavy equipment manufacturer, reduced C-suite officials by 102 as the company grappled with a prolonged industry slump, led by construction machinery unit Doosan Infracore Co.

Top steelmaker POSCO and Kumho Asiana Group, whose business ranges from airlines and construction to tires, each decreased the number of executives by 53.

Hyundai Heavy Industries Co., the world's top shipbuilder, let go 41 executives to help overcome an extended slump in new orders and other projects.

In contrast, Hanwha Group, whose main businesses include defense and solar power, hired 65 more senior executives to have 437 after acquiring Samsung's defense and petrochemical subsidiaries in a deal valued at 1.9 trillion won ($1.6 billion).

Retail giant Lotte Group also brought on 47 more officials after taking over Samsung's chemical units for about 3 trillion won in October. (Yonhap)