Heart-wrenching images of revered elephants and cattle eating plastic in Sri Lanka have prompted politicians to toughen pollution laws, but skeptical conservationists warn past bans were repeatedly ignored.

After an estimated 20 elephant deaths and countless other wild animals perishing due to single-use plastics in the past decade, officials say a law banning many such items is expected to come into force within weeks.

Bags, bottles and packaging are also blamed for clogging drains and causing urban flooding, as well as encouraging a surge in potentially deadly dengue — spread by mosquitoes that breed in stagnant water.