A fishing boat sank on Saturday morning near the town of Figueira da Foz in Coimbra County, SIC Notícias reported.
It is known that the incident took place around 07:00 local time (10:00 Moscow time).
According to available information, there were five crew members on board, four of them died, another sailor was hospitalized in serious condition.
The reasons for what happened are being investigated.
Earlier, in the vessel Favorit, which sank in the White Sea in early November, divers found the bodies of two crew members, who were considered missing.