The American Embassy in Dushanbe said Tajik citizens attacked a group of seven cyclists with a car and knives.
Two Americans were killed in Tajikistan over the weekend in what the U.S. Embassy there described on Monday as a "senseless" car and knife "attack" that targeted a group of seven cyclists.
Two other tourists were also killed, said Tajikistan's interior minister, Ramazon Rakhimzoda, during a news conference. One of these victims was Swiss, according to that country's foreign ministry.
The nationality of the other cyclists wasn't immediately clear.
Another person injured in the incident was stabbed and in stable in condition, Rakhimzoda added. A sixth person was in shock, he said, while the seventh cyclist wasn't harmed. He was released after being questioned by local authorities, Rakhimzoda said.
In a statement, the U.S. Embassy in Dushanbe said a car with Tajik citizens struck the foreign cyclists in Danghara, south of the former Soviet Republic's capital, on Sunday. The car's occupants got out and began stabbing the cyclists, the statement said, citing multiple unidentified sources.
"We condemn the senseless attack, offer our deepest condolences to the families of the victims, and wish the injured a speedy recovery," the statement said. "Because of privacy concerns, we are unable to share further details about the U.S. citizens."
Rakhimzoda said a chase with the suspects ensued. One was detained, another was killed and three are on the run, he told reporters.
ISIS claimed responsibility for the attack through a statement on Monday, though Tajik and American officials have not confirmed the group's involvement..
Rakhimzoda said investigators were still working to determine if the incident was a car accident, murder or terrorism.
A U.S. State Department spokesperson referred questions to Tajik authorities and said American officials were working with local investigators.