The victims were reportedly among the group of seven touring the country and riding in the Danghara district, about 150 kilometres south of the Central Asian republic's capital, Dushanbe. According to the media reports, a vehicle was driven into the group of cyclists who were then attacked by at least one person armed with a knife and a gun.
Two US citizens reportedly lost their lives as well as a Dutch and a Swiss national. Three others, from Switzerland, the Netherlands and France, were injured, one of them reportedly also from a stab wound.
"The tragic death of two citizens of the United States, one Dutch national and one Swiss citizen as a result of a car crashing into a group of cycling tourists on a Tajikistan motorway were met with great sadness and regret," Rahmon said in a telegram sent to the US, Dutch and Swiss leaders.
The Tajikistan's Interior Ministry said Monday that the suspects have been found and killed.
According to Reuters, thousands of people from the Central Asian region have joined Daesh terrorists in recent years. Several men from Central Asia were detained last year over ramming attacks in New York and Stockholm.