MOSCOW (AP) — Four tourists traveling through Tajikistan on bicycles were killed when a driver allegedly rammed his car into them and joined his passengers in going after the cyclists with knives, U.S. and Tajik officials said Monday.

Authorities in the ex-Soviet republic in Central Asia were considering an extremist plot among the possible motives for the attack, the country's interior minister said.

A Daewoo sedan plowed into a group of seven foreign bicyclists about 100 kilometers (60 miles) south of the Tajik capital, Dushanbe, on Sunday, according to local police. The people in the vehicle then "exited the car and stabbed the cyclists with knives," the U.S. Embassy in Tajikistan said in a statement Monday.

Four of the cyclists died and three others, including a woman from Switzerland, were injured, Tajik officials said.

Two of the victims were American, one was Swiss, and another was from the Netherlands, foreign and Tajik officials said. Tajik President Emomali Rahmon sent the leaders of each country a telegram expressing condolences Monday.

Interior Minister Ramazon Rakhimzoda told reporters that one of the survivors had knife wounds and police found knives and guns with some of the suspects. He described the car crash as "an attack," and said investigators were examining all possibilities, including a road accident, murder and terrorism.

Rakhimzoda said one suspect was killed while resisting arrest, his ministry said two suspects were killed and the U.S. Embassy reported three. The discrepancy could not be immediately explained.

Four suspects have been detained, according to the Interior Ministry.

The State Department issued a statement Monday condemning what it called a "senseless attack" and expressing "deepest condolences" to the families of the people killed. The department said it could not provide more information about the U.S. citizens due to "privacy concerns," but that U.S. officials were working closely with Tajik authorities.

Swiss Foreign Ministry spokeswoman Silvia Mueller said that while the circumstances of the crash were unclear, the Swiss government's travel advice for Tajikistan notes there is a risk of attacks and poor road travel conditions in the Central Asian country.

"Should it turn out to have been a terrorist act, this would be recorded in the travel advice," Mueller said.

The State Department encouraged Americans headed abroad to monitor government advisories for updated information on where it is safe to travel.

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Matthew Lee contributed from Washington.