The transfer was announced in a press conference in Braga, with Yasser expressing delight over the move which could be made permanent if the 24-year-old has a successful spell with the team from Porto.
The former Manchester City player said: "Boavista are a big club in Portugal and in Europe especially as they have won the Portuguese league before. I believe that the transfer will be a positive move and I will try my best to take advantage of it."
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