Sporting Lisbon have signed Portuguese international striker Helder Postiga from Porto on a three-year deal worth 2.5 million euros (3.8 million dollars), the club said Sunday.

The deal also sees Sporting's Diogo Filipe Viana go in the other direction, joining up with the Portuguese champion's reserves team.

Postiga (25) played for Porto from 1999 to 2003, before briefly moving to London club Tottenham in 2004. He returned to Porto in 2004 and the following season was loaned out to French first division side St. Etienne.

At the beginning of the year Postiga - part of Luiz Felipe Scolari's UEFA EURO 2008 squad - was sent to Greek first division side Panathinaikos. Since 2003 Postiga has been selected 32 times for the national side, scoring 10 goals.