Urea prices have risen by 10% in September and 30% since July after China banned the export of the fertilizer to keep domestic prices under control.
Petrovietnam Camau Fertilizer raised urea prices by 10% this month to VND11,200 per kilogram.
Petrovietnam Fertilizer and Chemicals Corp hiked prices by 4.8% to VND11,000.
Other chemical producers also effected similar hikes. Some such as HCMC-based Viet Au have raised prices to VND12,500.
Urea provides plants with nitrogen to stimulate leaf growth.
Phung Ha, deputy chairman of the Vietnam Fertilizer Association, said China, the biggest producer and consumer of urea globally, ordered some manufacturers earlier this month to stop exports and this caused prices of the key fertilizer to surge globally including in Vietnam.
Vietnamese farmers are buying fertilizers for their winter-spring crops, and the rising demand is exacerbating the rise in prices.
In the first eight months of the year, Vietnam imported nearly 2.5 million tons of fertilizers worth US$833 million, up 13% in volume but down 19% in value year-on-year.
Nearly half of the imports came from China.