TOKYO (Reuters) - Japan's economy grew at an annualised rate of 2.1 percent, government data showed on Monday, accelerating slightly from the previous quarter's growth backed by net export gains.

The preliminary reading for first-quarter gross domestic product compared with the median estimate of a 0.2 percent annualised contraction in a Reuters poll of economists. It followed a revised 1.6 percent expansion in October-December.

On a quarter-on-quarter basis GDP rose 0.5 percent, the Cabinet Office said, compared with the median estimate of a flat reading.

(Reporting by Tetsushi Kajimoto and Leika Kihara; Editing by Chris Gallagher)