This image shows a platform display at Sindorim Station, Nov. 30. Yonhap

Unionized workers at Seoul Metro, the city-run operator of the subway system in Seoul, went on a strike Wednesday, but few subway disruptions were reported during the morning rush hour, as replacement workers were mobilized.

Seoul Metro's two labor unions, representing some 13,000 workers, or 80 percent of the firm's entire workforce, kicked off the walkout early Wednesday morning, one day after their eight-hour negotiation with the company broke down without a breakthrough.

The strike affecting Subway Line No. 1 trough No. 8 marks the first of its kind in six years since the last one in September of 2016.

The unions have been protesting against Seoul Metro's plan to downsize its workforce by more than 1,500 employees through 2026.

The subway operator proposed temporarily putting off the restructuring plan during the negotiation Tuesday, but the unions rejected it as going against their previous agreement in 2021 that forswore any unnegotiated downsizing on account of a financial crisis.

This image shows the platform at the Gwanghwamun subway station, Nov. 29. Yonhap

As of 7 a.m., trains on Subway Line No. 2 through No. 8 had been running smoothly despite the strike, while delays of up to eight minutes were reported on trains on Line No. 1.

Seoul Metro was mobilizing retired employees and non-unionized workers as replacement workers to keep train operations at the normal level during the busy morning rush hour.

Train operating rates after the morning rush hour, however, will go down to 72.7 percent of the normal level, while trains will run at 85.7 percent of the normal level during the evening rush hour.

The Seoul city government also plans to increase bus operations during morning and evening rush hours to minimize any fallout from the strike.

The Seoul Metro unions predicted some 9,700 subway workers will join the strike on weekdays and 14,000 on weekends. (Yonhap)