TOKYO (AFP) - Japan's trade deficit more than quadrupled on year to US$3.7 billion (S$4.6 billion) in March, government data showed on Thursday, as a weaker yen inflated import costs.

The monthly trade deficit expanded to 362.4 billion yen (S$4.6 billion) from the year-before shortfall of 81.8 billion yen, finance ministry data showed.

The heavy deficit was still smaller than 480 billion yen economists predicted in a poll by the Nikkei business daily.

Exports rose 1.1 percent to 6.27 trillion yen while imports climbed 5.5 percent to 6.63 trillion yen.

The yen's average rate was 94.08 to the dollar in March against 81.04 in March 2012, meaning the value of the Japanese currency fell by 16 percent on year, the data showed.

A lower yen helps exporters but pushes up import bills.

Japan's fuel imports have stayed high as most its nuclear reactors remain off-line since the huge earthquake and tsunami in 2011 sparked the world's worst atomic accident in a generation.