Four babies have died and seven remain in a critical condition following a fire at a maternity hospital in Bucharest, the Romanian capital.

Authorities have launched an investigation into the incident which occured late on Monday.

Attila Cseke, the country's health minister, said the deaths were one of the "darkest tragedies in the history of Romania's health care system".

It was not immediately clear what caused the fire at the hospital, but Romanian media said it may have started due to a malfunctioning air conditioning unit.

The fire has provoked a wave of public indignation, throwing light on Romania's poorly funded and understaffed health system.

DNA identification

Cseke said 53 babies and 61 women, some in labour, had been evacuated from the Giulesti maternity hospital to other hospitals following the fire.

The minister said the hospital will stay closed until the investigation is finalised.

Raed Arafat, a health ministry official, said authorities will confirm the identity of all babies through DNA samples, after the plastic bracelets they wore for identification melted in the fire.

Thousands of doctors have left Romania in recent years for better paid jobs abroad.

Many hospitals are understaffed and cannot hire, as the government, facing a sharp economic downturn, is trying to keep the budget deficit down.

Reports of hospital patients who have to buy bandages, medicines and syringes abound in the Romanian media.

Even some doctors concede they lack things like surgical thread and so cannot perform surgery unless the patients buy it.

Gabriel Patrascu, a father visiting his wife at the hospital, told news channel Antena 3 that no medical staff were in the intensive care unit when the fire broke out.

Bogdan Marinescu, the maternity hospital manager, could not confirm the report.