SEOUL—Journalists from South Korea's largest television network, KBS, went on strike Tuesday, joining those from another state-owned network to protest alleged management interference in news coverage.

The other network, MBC, began the strike almost a month ago. Since then, MBC has cut its nightly news broadcast to 15 minutes from an hour and eliminated several other news programs.

About 650 KBS staff members, including 250 reporters, joined the strike, the workers' union said. The network's management said it would still produce news programs. The company employs nearly 5,000 people, including about 1,000 journalists.

The protests are the latest display of anger by journalists at the administration of President Lee Myung-bak. They blame his appointees for exercising tighter control of news content than at the start of their administration. The various media have a long history of tensions with their state owners, which also control sales of advertising for the TV networks.

"We want to secure an environment for impartial reporting, and we urge the chairmen and middle-ranking managers who only care for the government's favor to resign," Kim Seung-geun, manager at the National Union of Mediaworkers. It represents the employees at KBS, MBC and YTN, a state-affiliated cable-news network where employees have agreed to walk out on Thursday.