Russian forces took control of a Ukrainian border guard post in western Crimea on Sunday, trapping about 30 personnel inside, a border guard spokesman said.
He said by telephone that the Chernomorskoye base on the western edge of the Back Sea peninsula had been taken over without bloodshed at around six a.m. (0400 GMT).
The spokesman, Oleh Slobodyan, said Russian forces now controlled 11 border guard posts in Crimea.
Russian forces' seizure of the southern Ukrainian region, which began 11 days ago, has been bloodless. Ukrainian troops are trapped in a number of bases but have offered no armed resistance.