Gross domestic product expanded 5.46% in the three months through March, slowing from a 7.01% increase the preceding quarter and 6.12% growth last year, the General Statistics Office said Friday.

Vietnam traditionally releases data before the end of the reporting period and its statistics are often subject to significant revision.

“The drought and the intrusion of seawater into agricultural land has hurt farms in the Mekong Delta region,” said Can Van Luc, an economist with the Bank for Investment and Development of Vietnam. The Mekong Delta is Vietnam’s largest rice-growing area.

The size of the agricultural sector declined 1.3% in the first quarter from a year earlier, according to the GSO. It said industrial production grew 6.3% while retail sales of goods and services were up 9.1%.

Exports in the quarter rose 4.1% while imports fell 4.8%, the GSO said. A decline in Vietnam’s imports often points to a decline in aggregate demand, suggesting a future slowdown in manufacturing activity as firms import less materials and equipment for production.

However, Mr. Luc said it was too early to say whether the economy would slow this year, as Vietnam’s economic growth typically accelerates toward the end of the year.

“The country will have to try harder during the rest of the year to meet its economic growth target of 6.7%,” Mr. Luc said.

Vietnam’s economic expansion has gained momentum since growth fell to a recent low of 5.25% in 2012. The nation has benefited from a steady rise in investment from foreign investors seeking to cash in on several free-trade agreements, including the Trans-Pacific Partnership trade pact.

Disbursement of foreign direct investment in Vietnam in the first quarter is expected to increase 14.8% to $3.5 billion, according to the Ministry of Planning and Investment. FDI pledges in the three months through March more than doubled from a year earlier to $4 billion, the ministry said.

Disbursement refers to the actual amount of money spent, while FDI pledges indicate the size of future investment.

Vietnam aims for economic growth of 6.7% this year, a marginal increase from a 6.68% expansion last year. The country targets economic growth of between 6.5% and 7.0% a year during the 2016 to 2020 period, up from an average annual growth rate of 5.8% for the past five years.

By Vu Trong Khanh - The Wall Street Journal - March 25, 2016