SLOVYANSK, Ukraine — The Ukrainian government on Sunday for the first time sent its security services to confront armed pro-Russian militants in the country’s east, defying warnings from Russia. Commandos engaged in gunfights with men who had set up roadblocks and stormed a Ukrainian police station in Slovyansk, and at least one officer was killed, Ukrainian officials said.

Several officers were injured in the operation, as were four locals, the officials said. Russian news media and residents here disputed that account, saying the Ukrainian forces had only briefly engaged one checkpoint.

In either case, the central government in Kiev has turned to force to try to restore its authority in the east, a course of action that the Russian government has repeatedly warned against.