The international service of Bulgaria's national radio broadcasting organization, BNR, switched off its medium wave transmitters in the provinces of Kardzhali, Razgrad, Shumen and Targovishte, local media reported.
The radio station's three-hour daily Turkish language service will now only be broadcast in the northwestern province of Vidin, the reports said.
The recent sign-off has drawn criticism from the Turkish community.
"I have not been able to listen to the Turkish service since Jan. 1. I even took my radio into the store because I thought it was broken. That's when I learned about the shutdown," Fatme Mehmedali, a retired teacher in Kardzhali, said.
"So far, there has not been any official explanation as to why the service was shut down. We grew up listening to this radio, and we want it back," she said.
"The Turkish service dates back a long time. Back in the days, we had only two radios in the village where I lived; and we would all gather around the radios and listen to the Turkish broadcast. It was shut down at the beginning of the year, and nobody told us why," Mustafa Bayramali, a lawyer in Kardzhali, said.
BNR started its Turkish service in 1945. The service was shut down between 1984 and 1989 during the then-government's assimilation campaign against Turks.
There are 588,318 Turkish-origin inhabitants in Bulgaria according to the 2011 census results, which corresponds to 8.8% of the population, making it the country's largest ethnic minority.
BNR has yet to comment on the sign-off.
BNR's international service, Radio Bulgaria, broadcasts in 11 languages including Bulgarian, Albanian, Arabic, English, French, German, Greek, Russian, Serbian, Spanish and Turkish.