Champions in 2008 and 2012, with a maiden World Cup in between in 2010, Spain are assured of top spot in the section with 24 points after Santi Cazorla and substitute Paco Alcacer each struck twice in a dominant display in Logrono.
Vicente del Bosque's side are five points ahead of second-placed Slovakia, who lost 1-0 at home to Belarus, while Ukraine, who host Spain in Kiev on Monday, are third also on 19 points after they won 2-0 away to Macedonia.
Midfielder Cazorla, who earlier crashed a shot against the bar, put La Roja ahead three minutes before halftime when he followed up Pedro’s saved effort and drove the ball home.
Alcacer, who came on in the first half for the injured Alvaro Morata, made it 2-0 in the 67th when he ran on to a Cesc Fabregas pass and finished clinically past Jonathan Joubert.
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Alcacer scored his second goal, and Spain's third, from close range in the 80th minute after fine work from fullback Jordi Alba and Cazorla rifled the ball home from the edge of the penalty area five minutes from time to complete the rout.
"Finally we have managed it," Cazorla told Spanish television. "We couldn't let our guard down and I think it was a great win," the Arsenal midfielder added.
The victory came at a cost, however, as Morata was taken off on a stretcher after apparently sustaining damage to his right fibula and midfielder David Silva had to be replaced by Juan Mata after 11 minutes with what looked like an ankle problem.
Spain, looking to recover from their failure to get beyond the group stage at last year's World Cup in Brazil, will play their 12th straight international tournament in France.
Continental champions for the first time in 1964, they are unbeaten in 32 home qualifiers, winning their last 17 in the Euros since a 1-0 loss to Greece in Zaragoza in June 2003.
They last failed to qualify for the tournament in 1992 when it was held in Sweden.
(Writing by Iain Rogers, editing by Ken Ferris)
