"At noon on Friday they were laying an irrigation pipe when they were struck by wet rockfall during their work," Orif Nozimov, spokesman for Tajikistan's state emergencies committee, told AFP.
All of the victims were men between 20 and 30 years old, Nozimov said, noting that only two of the bodies were recovered by a rescue team.
Avalanches and mudslides are common in mountainous Tajikistan. In February, a single avalanche claimed six lives in the east of the Central Asian country.
Tajikistan's neighbour to the south, Afghanistan, has suffered its worst avalanche season in recent memory, with more than 200 deaths this past winter.