SEOUL (REUTERS) - South Korea's economy unexpectedly shrank in the first quarter, marking its worst performance since the global financial crisis, as government spending failed to keep up the previous quarter's strong pace and as companies slashed investment.

The shock contraction reinforced financial market views that the central bank is likely to make a U-turn on policy, shifting to an easing stance and possibly cutting interest rates to counter declining business confidence and growing external risks.

A worse-than-expected downturn in the memory chips sector hit first quarter capital investment, while slumping exports amid the US-China trade dispute erased gains from private consumption, the Bank of Korea said on Thursday.

Gross domestic product (GDP) in the first quarter declined a seasonally adjusted 0.3 per cent from the previous quarter, the worst contraction since a 3.3 per cent drop in late 2008 and sliding from one per cent growth in Oct-Dec, the Bank of Korea said on Thursday (April 25).

None of the economists surveyed in a Reuters poll had expected growth to contract. The median forecast was for a rise of 0.3 per cent.

"Government spending failed to keep up the bumper boost of the fourth quarter, especially for construction investment, while a drop in business investment was worse than expected due to a downturn in the chips sector," a BOK official said, adding there was also a strong base effect after solid fourth-quarter growth.

The grim data came a day after the Moon Jae-in government unveiled a 6.7 trillion won (S$7.9 billion) supplementary budget to tackle unprecedented air pollution levels and boost weak exports.

Capital investment tumbled 10.8 per cent, the worst reading since 1998, while construction investment inched down 0.1 per cent, the BOK said.

Exports fell 2.6 per cent quarter-on-quarter, a sharper drop than the 1.5 per cent decline in the previous three months.

Private consumption gained by 0.1 per cent due to a rise in demands for durable goods.

From a year earlier, Asia's fourth-largest economy grew 1.8 per cent in the January-March quarter, compared with 2.5 per cent growth in the poll and 3.1 per cent in the final quarter of 2018.