In the Second Round Group E battle between Portugal and Bulgaria, the contest was knotted at 38-38 midway through the third quarter when Joana Soeiro drilled a three-ball for the Portuguese.
Josephine Filipe added two free-throws to make it 43-38 and Portugal had their noses in front to stay.
However, Bulgaria pushed them until the end.
With four minutes to go, Bulgaria sharpshooter Radostina Dimitrova's three-pointer cut the Portugal lead to 54-52.
The Portuguese managed to stay on top and go to 3-0 with Hungary (2-1), Bulgaria (1-2) and Denmark (0-3) after them in Group E.
Hungary won their second game in Group E on Thursday, beating Denmark 67-43.
Fanni Csutorás led Hungary with 16 points.
The Hungarians took command from the off, outscoring the Danes 20-9 in the first frame.
By half-time, the lead was 37-15 and there was no way back for the Danes.
In Group F, Belarus and England won their games.
Belarus improved to 3-0 with a victory over Germany and the English prevailed 72-62 over Lithuania.
Mary Mihalyi's jumper cut the Belarus lead to 67-60 early in the fourth quarter and the Germans pulled to within six when Anneke Schlüter drained a three-ball.
But Belarus, who got 23 points and 12 rebounds from Maryia Papova, held their nerve and won by 15.
Shequila Joseph poured in 18 points for England in their 10-point triumph over Lithuania.
Cheridene Green had 16 points and 13 rebounds for England, who got a go-ahead three-pointer from Michelle Turner early in the fourth quarter.