UPDATE 1-S.Korea 2Q growth almost halves from Q1 as construction slows

(Updates with analyst comment, details)

* Q2 GDP +0.6 pct s/adj q/q (Reuters poll +0.6 pct)

* Q2 GDP +2.7 pct y/y (Reuters poll +2.7 pct)

* Construction output -0.3 pct q/q

* Exports -3.0 pct q/q, capex investment +5.1 pct q/q

SEOUL, July 27 (Reuters) - South Korea's economic growth almost halved in the second quarter of 2017 from the previous three months, the central bank estimated on Thursday, as construction sector activity that had supported growth earlier slowed.

Gross domestic product grew a seasonally adjusted 0.6 percent in the second quarter, the Bank of Korea said on Thursday, slowing from 1.1 percent growth over January to March.

It matches a median 0.6 percent increase forecast in a Reuters poll.

From a year earlier, the economy grew 2.7 percent in the April-June period, also on par with a median 2.7 percent forecast from economists in the poll.

Output from the construction sector declined 0.3 percent on-quarter in seasonally adjusted terms, the sharpest decline in two and a half-years after posting robust expansion throughout last year. It had expanded 5.3 percent in the first quarter from three months earlier.

"The construction sector is going through a soft landing after years of fast growth," said Kim Doo-un, an economist at Hana Financial Investment.

"Exports will continue to support growth in the second half, although the GDP data today shows its mostly the IT sector that is doing well."

Exports, which account for about 40 percent of GDP, fell 3 percent on-quarter, as shipments of petrochemical goods declined after surging earlier in the year.

Kim at Hana Financial Investment said surging prices of memory chips have been boosting the headline exports figures while the export volumes of other sectors have not been as robust.

Capital investment jumped 5.1 percent on-quarter, while exports fell 3 percent, the estimates showed.

Private consumption increased 0.9 percent from three months earlier after gaining 0.4 percent in the first quarter.

The central bank expects the economy to expand 2.8 percent this year, a little shy of the government's 3 percent forecast, as global demand for South Korea's memory chips, cars and petrochemical goods remain strong.

The BOK kept interest rates unchanged at a record low of 1.25 percent in July and most economists expect it to hold fire until next year.

($1 = 1,120.4900 won) (Reporting by Cynthia Kim; Additional reporting by Dahee Kim; Editing by Eric Meijer)