Australia thrashed Sri Lanka by an innings and 242 runs on day four of the opening test in Galle on Saturday.

Electing to bat, Australia amassed 654-6 declared in their first innings to take charge of the series opener at the Galle International Stadium.

They bundled out Sri Lanka for 165 in the first innings with Matthew Kuhnemann (5-63) leading the rout on a spin-friendly track.

Made to follow on, Sri Lanka were all out for 247 to succumb to their heaviest-ever Test defeat. Jeffrey Vandersay (53) was the top scorer for Sri Lanka before being the last man out.

Nathan Lyon and Kuhnemann took four wickets apiece.

The second test begins on Thursday. (Reuters)