Thousands of Rwandans have taken the day off work to pick up plastic bags as part of a government attempt to clean up the environment.
Shops have been banned from giving plastic bags to their customers and police are reportedly stopping plastic-bag users in the street.
Some supermarkets have been closed down for flouting the ban, said environment minister Drocella Mugorewera.
"We want people to use traditional baskets instead," she said.
The government has always been keen to keep Rwanda clean and correspondents say the capital, Kigali, is much cleaner than other African cities, where thin blue plastic bags can been seen in fields and on trees fluttering in the wind.
"We have a real problem with plastic and we are linking this with our efforts to protect our rivers and lakes," Ms Mugorewera told Reuters news agency.
But some shop-owners feel the government is being too heavy-handed.
"The government is being unfair to small business owners, some of us cannot afford expensive packing materials, our clients are running away," said one kiosk owner.