ZIMBABWEAN authorities say at least 81 elephants have been killed for their ivory tusks by poachers using cyanide poison in water holes in a vast western national park.

Tourism Minister Walter Mzembi, in Harare on Tuesday after touring Hwange National Park, said more elephant carcasses were discovered after a first count of more than 40 earlier in the month.

Wildlife department officials said industrial cyanide, used in gold mining, was put in the park's remote water holes, killing smaller animals drinking there and vultures and other predators feeding on the dead animals.

Nine alleged poachers were arrested after rangers tracked them to a cache of ivory hidden in the park.

Zimbabwe's state media reported Tuesday that newly-appointed environment minister Saviour Kasukuwere has vowed harsher jail penalties for poachers.