The Korean Railway Workers' Union kicked off a work-to-rule protest on Thursday.

The union said on Wednesday that its members are staging the eight-day collective action in protest against the transport ministry's push for the privatization of the railways and the preferential treatment of high-speed train operator SR Corporation.

The union is demanding an expansion of the KTX service as well as a meeting with the transport minister to discuss measures to further develop the railways, such as integrating the SRT and KTX bullet train services to help with seat shortages and fare costs.

During this period, the operation of four Mugunghwa trains will be suspended and while the KTX is expected to run normally, the Korea Railroad Corporation has warned of possible delays and asked the public to check on the status of their trains in advance.