Hungarian Prime Minister Viktor Orban has ordered an inquiry into the deaths of eight premature babies in five days at a hospital in the northeastern city of Miskolc.

Health state secretary Miklos Szocska said alongside the announcement of the inquiry late on Monday that the National Surgeon General's office was doing all it could to find out why the eight premature babies died. He told Kossuth radio on Tuesday that the babies died between Aug. 5 and Aug 10.

"There are investigations under way to reveal any potential infection," Szocska said in a video posted on the government's official website, adding he would not yet close the specialised department at the Borsod-Abauj-Zemplen hospital which treats hundreds of prematurely born babies each year.

Mortality rates in the department have dropped to around 30 per year from around 50 over the last two years, Szocska said.

"There are several hypotheses: the increase (in fatalities) gives reason for concern, therefore we need to reveal thoroughly what happened, whether there is any link (between the deaths) and what could be the cause," he said in the video.

Szocska said lab tests would take about a week and he expected results from the inquiry in two weeks.

The hospital's director has been suspended.

A police spokeswoman said on Tuesday that a criminal investigation had been opened but declined to give any details.