David Silva and substitute Cesc Fabregas also scored second-half goals yesterday as the defending champions improved to four points in Group C, the same as co-leader Croatia.
Spain dominated the tempo and scoring opportunities through its quick combinations. Torres, who scored in the Euro 2008 final, put Spain ahead early after dispossessing Richard Dunne inside the area and scurrying past Stephen Ward before sending an angled shot over goalkeeper Shay Given in the fourth minute.
"We wanted to win, to make a better impression than we did against Italy," Torres said. "You have to enjoy every moment, every game. I started again, scored two goals and enjoyed playing again with my teammates."
The goal marked the start of Spain's assault on the Irish, who had started well with Simon Cox forcing Spain goalkeeper Iker Casillas into a tricky save in only the second minute. But Spain's combination passing got better, leaving Ireland in a constant chase.
Spain midfielders Xavi Hernandez and Xabi Alonso exploited every crack through the middle with pinpoint passes that were either spoiled by poor finishing, blocked shots or saves.
"For the vast majority of time, we were chasing shadows," Ireland midfielder Keith Andrews said.
Silva was a continuous threat inside the area before finally converting early in the second half. The Manchester City forward gathered the ball inside the area in the 49th before showing some patience by rolling a left-footed shot around two defenders and through Dunne's legs and out of the reach of Given.