Barcelona eased into the last 16 after record-chasing Lionel Messi fired a first-half double as the favourites rediscovered their European verve to overcome Spartak Moscow.
Full-back Daniel Alves opened the scoring in the 16th minute and Messi added two more in the space of 12 minutes before half-time with his 79th and 80th goals of the calendar year.
The Catalans, who also secured top spot in the group after shrugging off the 2-1 defeat at Celtic two weeks ago, controlled the tempo with their famous tiki-taka passing game on Moscow's slick artificial turf and often picked holes in Spartak's defence.
"We couldn't allow what happened at Celtic to happen again," said Messi. "We knew we had to come out strongly right from the start because it's always tough to play away in this competition and even more so given the state of the pitch.
"Obviously the fact we didn't concede is a boost for everyone, especially when we have been letting in too many goals recently."
Brazil international Alves beat Spartak goalkeeper Andriy Dykan with a low blast from outside the box after the Russians failed to clear the ball.
Messi doubled the lead 11 minutes later, firing into an unguarded goal after Dykan did well to stop the initial shot by Andres Iniesta. The Argentinian wizard made it 3-0 after rounding Dykan and rolling the ball into an empty net following a great through pass by Pedro.
Messi was denied a hat-trick late in the game when he had the goal at his mercy after rounding the keeper only for a defender to nick the ball at the last second. Cesc Fabregas, Iniesta and Pedro also missed good chances.