Competition intensifies in Seoul as parties vie for control of the assembly.

South Korea's ruling and opposition lawmakers campaigned throughout Gangseo in western Seoul over the long holiday weekend, as the district will choose a new chief in a by-election next week.

With the general election still six months away, the by-election in Gangseo-gu on October 11 will provide insight into voter sentiment in Seoul, a 40-seat hinge district that can determine which party wins control of the National Assembly.