In the first accident, a passenger bus collided with an approaching truck at around 4 p.m. Friday, killing two women and a one-year-old baby on the bus, Tuoi Tre newspaper said, citing traffic police in Nghe An Province, some 300 km (190 miles) south of Hanoi.
The bus was badly damaged and several other passengers had to be rushed to hospital with injuries.
About an hour later a container truck lost control after one of its tyres exploded, slamming into a motorbike and killing three men aboard around half a mile from the site of the first accident.
Tuoi Tre said the three were driving home after watching the truck-bus crash.
At least 2,114 people were killed in more than 4,800 traffic accidents across Vietnam between January 1 and March 15, down 3.6 percent in terms of casualties from a year ago, based on government data, suggesting an average 23 people were killed on the road every day in the first quarter.