Subway service delays were reported in the capital region on Tuesday as the Korean Railway Workers’ Union entered the second day of its work-to-rule protest.

According to the Korea Railroad Corporation(KORAIL), as of 10 a.m., 150 out of 653 electric trains, or 23 percent, reported delays of at least 20 minutes.

The delays affected Seoul subway lines 1, 3 and 4, as well as the Suin-Bundang and Gyeongui-Jungang lines.

The high-speed KTX and other trains are operating normally.

An official at KORAIL said operations for some destinations are being adjusted or suspended as part of efforts to minimize delays.

Unionized rail workers, who launched the work-to-rule protest on Monday to call for a bigger workforce and a wage hike, are expected to call a general strike Thursday if their demands are not met.