BUENOS AIRES—Supermarkets and electronics retailers say Argentina's government has ordered them to stop advertising in the country's top newspapers, in a bid to weaken independent media companies as President Cristina Kirchner turns to increasingly unorthodox policies to prevent inflation from derailing an ailing economy.

The order, confirmed by retailers and newspapers but denied by government officials, comes after retail executives say price-control czar Guillermo Moreno pressured them earlier this week to agree to freeze...