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.

"We want to create an awareness about the responsible use of plastics," Anil Jasinghe, the country's top environment official, told AFP.

Jasinghe said regulations to be published soon will outlaw the sale of a string of single-use plastic items, including cutlery, cups, drinking straws and plastic flower garlands.

But it is not Sri Lanka's first attempt to tackle the problem.