Newcastle United have turned Mikel Merino's loan move from German side Borussia Dortmund into a permanent deal with the midfielder signing a five-year contract, the Premier League club said on Friday.

The 21-year-old Spaniard joined Newcastle on a season-long loan from Dortmund in July and has played in all seven of their league games so far.

"I'm really happy to be here, and for this part of the contract to finally be official," Merino told Newcastle's website.

"I'm focused on my displays and improving myself, and I'm really happy to have signed this contract."

Rafa Benitez's promoted side are ninth in the table and travel to Southampton, three places below them, on Sunday.