SEOUL (Reuters) -- Shares of South Korean automakers such as Hyundai Motor surged today after the country agreed a trade deal with the United States, raising the prospect of increased sales at home and in its top export market.

Hyundai Motor Co. ended up 3.33 percent, compared to a 0.48 percent gain in the broader market, while Kia Motors Corp. closed 5.51 percent higher and Ssangyong Motor Co. gained 1.46 percent.

"The deal with the world's top economy is expected to lift sales of South Korean automakers at home and in the United States," said Stephen Ahn, an auto analyst at Woori Investment and Securities.

The United States and South Korea today agreed the biggest U.S. trade pact for 15 years after nine months of negotiations.

The United States will immediately remove tariffs on 3.0-liter or smaller cars and auto parts from South Korea. It will also eliminate tariffs for cars bigger than 3.0 liters in three years and for pickups in 10 years.

South Korea will simplify auto taxes, setting all auto taxes at 5 percent in three years for both imported and domestic cars, which will lead lower taxes.

Analysts said lower taxes in South Korea would likely boost South Korean or Japanese automakers rather than U.S. cars as consumers in Asia's third-largest economy prefer luxury models such as Toyota Motor Corp.'s Lexus rather than U.S. models.

"The deal will lift local auto sales as lower taxes are expected to bolster purchasing power and on weak competitiveness of U.S. cars," said Song Sang-hoon, an analyst at Heungkuk Securities.

But the impact of the tariff removal on U.S. sales of South Korean automakers was seen as limited as Hyundai already has a factory there and Kia is also building a plant.

Auto sales abroad, which account for 10 percent of total South Korean exports and are an important growth driver in Asia's third-largest economy, rose an estimated 5.3 percent in value in March from a year earlier, commerce ministry data showed.

Combined sales by South Korea's five automakers rose 3 percent to 461,822 vehicles in March from 448,278 units a year ago, and were up 24.1 percent from February's 372,024 units, according to company data.

Exports grew 2.7 percent to 356,647 vehicles from a year ago and domestic sales gained 4.1 percent to 105,175.

But some analysts said stronger sales to the United States weren't assured yet, noting that a slowdown in the U.S. economy might hit demand in the world's top auto market.

Hyundai, the world's sixth-largest automaker along with its affiliate Kia by sales volume, saw its March sales fall 1.8 percent to 229,692 vehicles from a year ago with exports down 3.7 percent.

Its U.S. sales fell about 3 percent, according to company officials.

"It is inevitable U.S. sales of South Korean auto makers may be under pressure if overall consumer sentiment is hit," said Cho Soo-hong, an analyst at Dongbu Securities.