Kenyans visiting Karura Forest and Nairobi National Park will no longer be allowed past the gates with their drinking water if it is in disposable plastic bottles.
The prohibition applies to the polyethylene terephthalate disposable water bottles commonly used by bottlers or any other plastic material.
Visitors are, however, allowed to carry their heavy-duty reusable plastic bottles.
Environment Cabinet Secretary Judi Wakhungu made the declaration at Karura Forest on Tuesday. A similar ceremony will take place for the park at a later date.
Prof Wakhungu said the prohibition would be extended to all other protected areas and forest reserves in due time to rid them of plastics.
"To begin with, we want all protected areas to be plastic free," she said. "I will then announce that all our protected areas must be plastic free because we have seen it working here in Karura."
The Karura ban is an initiative by the Friends of Karura group that was introduced immediately after the ban on plastic bags last month.
"At the Karura gates, you will be asked to declare any plastics you have with you. And if you have any, you'll kindly be asked to put it in a container provided at the gate," said the CS. "That way, we will ensure that visitors do not litter the forest when they leave."
She said that soon, the government will ban disposable plastic bottles nationally, adding that discussions with manufacturers and recyclers were under way.
"It has only been three weeks since the ban on plastic bags and we have seen significant progress. Let's see how we fare in six months. Kenyans who do not want to use plastic bottles have a choice to start using the alternatives," she said.
Ms Wakhungu initiated the plastic bags ban that took effect on August 28. It has been hailed as a great success, she said she had been receiving applause from across the globe for the move.
"It is a good thing that we're getting used to the ban on the single-use plastic carrier bags but also eventually we will have to adjust and also do away with the plastic bottles. Kenyans have requested that. We are not ready yet but we're getting there," she hinted.
Billions of single-use plastic bottles especially water bottles and cups are thrown into landfill sites every year and the CS noted that they were keenly observing the industry to see how manufacturers recycle-to-reuse the bottles and other single-use plastic materials.
She said the project was a work in progress.
Kenya Forest Service Director, Emilio Mugo said he had already directed all field people around the country to enforce ban on any plastics around forest reserves and protected areas under their mandate. "It is something we're already prepared for and are implementing even before the CS issues the directive for other protected areas."