Twenty-seven trains were delayed for at least 20 minutes on Thursday, the second day of a work-to-rule protest at Seoul Metro, which manages subway lines 1 to 8.

According to the city-run operator, the on-time rate for a total of three-thousand-189 trains rose from 96 percent on the first day to 99 percent.

The delayed trains were all on Line No. 1, which is under joint management with the Korea Railway Corporation(KORAIL), whose workers are also staging a work-to-rule action.

All trains were running on time as of 8 a.m. Friday.

The labor union at Seoul Metro, which is calling for a wage hike of at least five percent and an increased workforce, plans to stage a general strike on December 6 if its demands are not met.

As the Korean Railway Workers’ Union enters the fifth day of its protest, KORAIL said 18 trains, mostly on the Gyeongui-Jungang line in the capital area, were delayed for at least 20 minutes between 5 a.m. and 9 a.m. Friday.

Calling for a bigger workforce and a wage hike of two-point-five percent, the union intends to begin an indefinite strike December 5.