The 230-kilogram, 1.5-meter-long device was discovered by chance by a local fisherman, about 10 meters from the bank of the Thach Han River.
The local police were alerted and cordoned off the area until experts from the Bomb and Mines Advisory Group arrived at the site and took it to a safe place, where it was dismantled.
With four-fifths of its territory plagued with bombs and mines, Quang Tri is the Vietnamese province most exposed to this latent threat.
Since the end of the war in 1975, over 3,400 people have been killed by accidental contacts with dreaded UXOs (unexploded ordnance) and 5,100 others have been seriously wounded or disabled for life.
The US military used over 15 million tons of bombs and mines in Vietnam, four times the number used in World War II, making Vietnam one of the most contaminated countries with such devices.