Arsenal sign Fabio Vieira from Porto.

LONDON -- Arsenal completed the signing of highly-rated Porto midfielder Fabio Vieira in a 40-million-euro ($42 million) deal on Tuesday.

The 22-year-old has emerged as one of Europe's most gifted young stars after coming through the Portuguese club's youth system.

He played a key role in Porto's domestic double last season, scoring seven goals and providing 16 assists in all competitions.

Praising Arsenal's third signing of the transfer window, Gunners manager Mikel Arteta said: "I am very excited that we have identified and signed such a special talent.

"Fabio is a very creative player that will bring high quality and versatility to our attacking play."

Porto said last week that Vieira, who was voted player of the tournament at last year's Under-21 European Championship, would move to London after both clubs agreed a deal in principle.

The Portuguese champions said the Gunners would pay an initial 35 million euros for the midfielder, with the rest in potential add-ons.

Arsenal did not specify the...