After the officers had stopped, the armed men fired warning bursts of automatic weapons fire into the air to make other unidentified vehicles halt, said an Associated Press reporter. No injuries were reported.
The multinational group of military officers from the Organisation for Security and Cooperation in Europe was attempting to enter the embattled peninsula from the north.
The armed men told them they had no authorisation to enter Crimea.
The OSCE mission will likely return to the Ukrainian city of Kherson where it had spent the night, the AP reporter said.