SEOUL (AFP) - South Korea's industrial output fell 3.7 per cent in January - the biggest monthly decline for six years - due to slowing production in auto and machinery production, state data showed Monday.

The 3.7-per cent fall in production of mining, manufacturing, gas and electricities followed a 3.0-per cent increase in December.

While the December monthly growth rate was the highest for five years, the January decline was the sharpest since December 2008 when output dropped 10.5 per cent.

Production of cars shrank 7.7 per cent from a month earlier and machinery production also tumbled 6.8 per cent.

Retail sales fell 3.1 per cent on-month. The country's 80-per cent hike in cigarette prices that took effect in January played a role in dampening consumption, Yonhap news agency quoted a finance ministry official as saying.

Investment also sagged 7.1 per cent due to falling spending by carmakers and machinery firms.