South Korea's car exports shrank more than 4 per cent from a year earlier in May as outbound shipments to the United States sharply dropped on Washington's hefty tariffs on imported vehicles, data showed on Tuesday.

The value of outbound shipments of automobiles came to $6.2 billion last month, down 4.4 percent from a year earlier, according to data from the Ministry of Trade, Industry and Energy, reports Yonhap news agency.

The figure marks the second-highest export value for any May but also the second consecutive month of decrease.

In terms of volume, exports fell 3.1 percent on-year to 247,577 vehicles. However, shipments of eco-friendly vehicles went up 10.2 percent to a new monthly high of 75,000 units thanks to strong demand for hybrid cars.

The ministry attributed the overall decrease in auto exports to a base effect from a record monthly figure posted a year ago and impacts of the U.S. Donald Trump administration's 25 percent tariffs on all imported cars and auto parts.

Exports to the U.S. slid 27.1 percent on-year to $2.5 billion in May, with broader shipments to the North American region dipping 22.3 percent to $3.08 billion.

Shipments to the Middle East also fell 7.2 percent to $391 million.

On the other hand, exports to the European Union and Asia increased 28.9 percent and 45.1 percent to $837 million and $683 million, respectively.

At home, sales of automobiles rose 0.4 percent on-year to 142,000 units in May, while domestic production went down 3.7 percent to 359,000 units.

Notably, monthly sales of eco-friendly vehicles surpassed those of internal combustion vehicles for the first time here.

More than 73,000 units of eco-friendly vehicles were sold in South Korea in May, up 39 percent from a year earlier, according to the ministry.