More than 260 firefighters, almost 100 emergency vehicles and two helicopters were deployed to the scene near Carvalhal, in the central Castelo Branco district.

The accident occurred around 0845 GMT.

The dead toll initially stood at four women and six men, all between the ages of 50 and 70, according to medical teams at the site, while six others were in a serious condition with head and chest injuries.

One of the injured later died in hospital in nearby Coimbra. Among the dozens of injured were seven children.

Rescue team leader Rui Esteves said the bus was travelling from Portalegre in central Portugal to the northern city of Santa Maria da Feira.

He said the identities of the victims were not all known but that all 43 were believed to be Portuguese.

While Esteves did not give further details about the accident, the mayor of the nearby town of Serta, Jose Nunes, blamed it on roadworks and weather conditions.