HANOI, June 29 - Vietnam's annual economic growth rate quickened to 6.17 percent in the second quarter, government data showed on Thursday, as strong manufacturing growth offset a continuing slump in mining production.

In January-March, the growth rate was 5.15 percent, the lowest in three years. Vietnam's target for full-year 2017 growth is 6.7 percent.

To achieve that, there needs to be 7.4 percent expansion in the second half, according to Ha Quang Tuyen, head of the General Statistics Office's National Accounts Department.

In the second quarter, manufacturing and processing growth surged to 12.09 percent from a year earlier, compared with 8.6 percent in the previous three months.

Tuyen said a main factor for the rise was ramped up production by South Korea's Samsung Electronics Corp , Vietnam's biggest foreign investor.

Construction, real estate and commerce also contributed to the pick-up in the second quarter, Tuyen said.

Mining production continued to decline from a year earlier, but the decrease was less severe than in the first quarter after two major state companies increased coal and crude oil output, Tuyen added.

But lower prices for both commodities posed threats to growth, he said.

Tuyen said investment, manufacturing, construction and tourism will be key drivers of the economy the rest of this year.

Falling prices of some commodities and higher interest rates in the United States pose challenges, he said.