Domestic car sales by the five Korean carmakers soared 17 percent to 148,888 units in March from the same period last year, bolstered by the "new car effect" and the extension of tax cut benefits on car purchases by June, data compiled by each company said. But the five companies with production lines here -- Hyundai, Kia, General Motors Korea, Renault Samsung and Ssangyong Motor - saw their overseas sales drop 4.3 percent on-year last month, the data showed.