Seoul's unionized city bus workers announced plans for industrial action on Wednesday, including a strike or work-to-rule. 

According to the Seoul intracity bus union under the Korean Automobile and Transport Workers' Federation, the industrial action won support from 84-point-nine percent of its members, or 96-point-three percent of members who cast a vote on Monday.

The union and management have held nine rounds of negotiation, as well as a meeting mediated by the Seoul branch of the National Labor Relations Commission over a wage hike, but the two sides have yet to reach an agreement.

Should the second mediation scheduled for Tuesday fail, the union intends to strike or work-to-rule the following day.

The Seoul Metropolitan Government plans to increase subway operation, extend the rush hour by one hour, and run free shuttle buses to and from subway stations should the bus workers take collective action.