Hundreds of doctors in Croatia have been implicated in a corruption probe targeting a local pharmaceutical firm whose management and other workers were detained Monday, a minister said.

Health Minister Rajko Ostojic told AFP that the employees of Farmal, based in the northern town of Ludbreg, had been detained on suspicion of corruption and said the investigation would now focus on doctors.

"Actions will now successively, in order not to jeopardise (the) health system, target some 350 primary care doctors suspected of being involved," he said.

Ostojic did not elaborate on the ongoing operation, led by the country's anti-graft bureau, but national television HRT reported that the doctors are suspected of being bribed to prescribe Farmal drugs.

According to Farmal's webpage, it produces generic drugs, including antibiotics, as well as drugs to treat cardiovascular, gastroenterological, bone, muscular and neuropsychiatric diseases.

The fight against corruption is key for Croatia's bid to join the European Union, due in July 2013.

According to a press release posted online, the German group Dermapharm AG in January 2011 acquired a 95-percent share in Farmal.

Dermapharm's press office did not immediately respond to an emailed request for comment.

HRT said about 30 Farmal employees including its head Drazen Dedi had been detained.

Croatia's anti-graft bureau, USKOK, did not immediately provide any details about the operation dubbed "Hippocrat," the first of its kind in the former Yugoslav republic.

Croatia has about 5,000 primary care doctors.

Ostojic hailed the action as a "good day for the whole Croatian society."

"The fight against corruption is our crucial interest, not only in health but in all segments of our society," he said.