TOKYO (REUTERS) - Japan's exports surged in May by the fastest in more than two years on bigger shipments of cars and steel, an encouraging sign that robust overseas demand will support economic growth.

The 14.9 per cent annual increase in exports in May was below the median estimate for a 16.1 per cent annual increase but was nonetheless the biggest rise since January 2015.

Exports are likely to continue rising at a steady clip as overseas economies show increasing signs of strength, which should help Japan's economy extend its recent run of solid expansion.

Japan's exports to the United States rose 11.6 per cent in May from a year ago, the fastest increase since July 2015, due to an increase of shipments of autos and auto parts.

Exports to China increased 23.9 per cent year-on-year in May, following a 14.8 per cent annual increase in April. Larger shipments of flat panels and semiconductor manufacturing equipment drove the gains in China-bound exports.

Japan's imports rose 17.8 per cent in the year to May, versus the median estimate for a 14.8 per cent annual increase, as a rise in the price of oil from a year ago pushed up the value of imports.

The trade balance came to a deficit of 203.4 billion yen (S$2.52 billion), versus the median estimate for a 76.0 billion yen deficit.

Policymakers and economists have become more optimistic about Japan's prospects this year as an increase in factory output and a tightening labour market show the economy is poised to extend its recent growth.