The Peruvian-flagged vessel carrying 20 people of various nationalities, embarked from the city of Iquitos in Peru en route to the town of Santa Rosa, when the accident occurred along a Colombian stretch of the river.
Military officials said the boat capsized near the town of Isla Loreta, along a Colombian stretch of the Amazon late Sunday or early today.
Officials said they have been able so far to rescue 15 of the tourists, who hailed from Russia, the United States, Chile, Peru, India and Colombia.