The winger helped Spain win the European Under-21 Championship in June and scored in a 2-1 victory over Germany in the final.
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Croatian outlet Sportske Novosti claim Dinimo want to keep Olmo for the rest of their Champions League qualification campaign.
And that reportedly saw the club reject advances from Manchester United, Everton, Wolves and Bayern Munich over the summer.
Former Barcelona trainee Olmo teased a move to the Premier League last month.
He said: “[My future?] We are talking about the best leagues in the world and they all have positive things.
“LaLiga is something more special because for me it is home, with my people.