In the meantime, GSO says, 2.8 million foreigners arrived to the country by air, up 14.2 percent against 2011.
China topped the list with 682,000 tourists, accounting for 22.3 percent of the total foreign visitors to Vietnam in the first five months.
The Republic of Korea saw the sharpest year-on-year increase in the number of visitors to Vietnam with 41.3 percent, followed by Thailand with 28.6 percent.
However, the total number of international visitors to the country in June hit only 417,000, down 8.6 percent compared to May and 28.6 percent against June 2011.
The Vietnamese tourism sector aims to welcome 6.5 million foreign visitors in 2012.