Raul Meireles opened the scoring after 29 minutes at the Green Point Stadium before Portugal netted three times in the space of seven second-half minutes.
Goals from Simao Sabrosa, Hugo Almeida and Tiago ensured the lowest-ranked team in the tournament were eliminated before efforts from Liedson, Cristiano Ronaldo and Tiago again in the last 10 minutes added a real gloss to the scoreline.
It means that even if Portugal lose their final game to Brazil, the Ivory Coast will need to beat North Korea and overturn a nine goal differential.
The game could not offer the drama of 44 years ago when North Korea took a 3-0 lead over Portugal in the World Cup quarter-final at Goodison Park before losing 5-3 - but a lively opening period saw 15 attempts on goal.
Ricardo Carvalho saw an early header hit the post before Meireles, a constant threat with his runs from midfield, broke the deadlock.
The Porto man timed his run to perfection and lashed his shot under the outrushing Ri Myong-guk after a great through ball by Tiago.
Indeed Meireles should have had a second before half-time after Pak Chol-jin's clearance hit An Yong-hak and the ball fell to him, but he dragged his effort wide from close range.
Korea did have a golden chance to open the scoring after 18 minutes when a powerful diagonal drive from Hong Yong-jo was pushed away by Eduardo and straight to Pak Nam-chol - but he failed to keep his header down from point-blank range.
Cha Jong-hyok and An Yong-hak also had decent strikes from distance as Korea showed far more adventure than they did in their opening 2-1 defeat to Brazil.
But they were overwhelmed in the second half and Portugal extended their lead after 53 minutes through the best team goal of the tournament.
A cross from the right was chested down by Almeida, he combined with Meireles who slipped in Simao and the Atletico Madrid winger calmly slotted his finish between the legs of Ri Myong-guk.
Three minutes later it became three with the impressive full-back Fabio Coentrao bursting down the left and his pinpoint cross was headed home by Almeida.
Almeida was one of four changes made to the starting XI by Carlos Queiroz after the disappointing goalless draw against Ivory Coast and another of the new faces, Tiago, added the fourth.
Ronaldo sprung the offside trap down the left and pulled the ball back to the former Chelsea midfielder who sidefooted his shot into the back of the net.
Portugal threatened to run riot with Meireles missing a gilt-edged chance from eight yards, Coentrao dinking the ball marginally wide and Ronaldo cutting inside and unleashing a thunderbolt that flicked off the top of the crossbar.
Liedson did add the fifth, nine minutes from time, as he lashed a volley into the back of the net with virtually his first touch after Ri Kwang-chon made a complete hash of Duda's cross from the left.
Another defensive calamity saw Ronaldo break his streak of 12 international matches without a goal, Liedson nipping in to steal the ball before the Real Madrid star saw his shot bounce back off the keeper and roll down his back and neck before he tapped into an empty net.
Tiago completed the rout a minute from time as he planted his header into the far corner after a cross from the left by Miguel Veloso and Portugal will go into Friday's Group G finale against Brazil with real confidence and a chance to top the group.