South Korean online mall sales growth has decelerated as competition grows more fierce, government data shows.

There was a 3.6 per cent increase in the combined revenue of 26 offline and online retailers to 10.22 trillion won (US$9 billion) in July, according to the Ministry of Trade, Industry and Energy. This gain marks a deceleration from 7.2, 6.3 and 7.2 per cent growth posted in April, May and June respectively.

The slowdown is attributed largely to fewer sales on online open markets such as eBay and 11st.

Sales at 13 major online shopping malls rose 4.4 per cent last month, following double-digit growth for five straight months since February. Meanwhile, the sales of the 13 offline retailers, including department stores, discount chains and convenience stores, rose 3.2 per cent on-year on the back of strong performance by convenience stores.

Convenience stores saw their sales rise 11.1 per cent last month, with hypermarket chains posting 1.7 per cent growth and department stores having a 1.3 per cent revenue slide.