Diesel prices have skyrocketed about 105 percent from February 26, two days before the US and Israel launched strikes on Iran. The government raised the price to 39,660 dong ($1.50) per litre Wednesday, up from 19,270 dong last month, trade ministry figures showed.
The price of 95-octane petrol also jumped nearly 68 percent over the same period, from 20,150 dong to 33,840 dong.
A surge in oil prices since the start of the conflict has sent fuel costs spiralling and sparked fears of shortages around the world.
Vietnam has recently asked for fuel support from several countries, including Qatar, Kuwait, Algeria and Japan, and on Monday signed a deal with Russia on oil and gas production in both countries.
The country's finance ministry proposed on Tuesday halving the environmental protection tax on gasoline and diesel.
Hanoi resident Nguyen Van Chi said Wednesday he had not driven his truck in the past two weeks, instead opting to cycle as much as possible.
"With this unbelievable price of diesel, I cannot even sell my truck as no one is going to use it," the 54-year-old businessman told AFP.
