Sumatra's endangered elephants and tigers should get a boost from an Indonesian government move to expand one of their last havens, a four-year-old national park on the island, conservation body WWF said on Thursday.

But WWF warned that increased efforts would be vital to ensure that poaching and other illegal activities -- like unsanctioned logging and settlement -- did not continue in the park, Tesso Nilo in Sumatra's Riau Province.