second crushing victory
within a week - along with Webber's comfortable second place - confirms the impression that Red Bull have made a significant step forward with their car and that the German is on course for a third consecutive title.
"Fantastic. I'm very happy," said Vettel. "I tried hard to push, Mark was always on my toes. We had two brilliant pit stops.
"The only mistake I had was I locked up the front right on the way in. Fortunately I had a good lead and I could control the gaps. We were a little bit worried about the tyres because there has been a lot of locking.
"The guys have been flat out, not much break between Japan and here we have done another step on the car, and hopefully we can carry that through to the next races."
Ferrari were comfortably clear of the rest, with Massa taking fourth place close behind Alonso in the Brazilian's most competitive performance of the season. He is expected to be confirmed at the team for 2013 in the forthcoming days.
"We have to be happy with the performance today," said Alonso. "We were third and fourth just behind Red Bull who at the moment are difficult to beat.
"We overtook McLaren in the constructors' championship, which we didn't expect. So we are moving in the right direction. We just need a little step to compete with Red Bull and it's going to be a beautiful last four races."
But they could do nothing about the Red Bulls ahead as Vettel, from second position on the grid behind Webber, moved into the lead on the run down to the first corner and never looked back, only briefly losing the lead during the first pit stops.
“I'm very happy. I tried hard to push, Mark was always on my toes”
Red Bull became increasingly anxious about the wear of Vettel's right-front tyre in the closing laps and warned him to back off in certain corners.
But he managed it well - as did Webber in a similar situation behind him - and Alonso had to settle for third.
After their second and final stops, Massa closed up on Alonso, but was told by his race engineer Rob Smedley that he was "a little bit too close to Fernando" and to back off a little.
It became clear later on that Alonso had been conserving his tyres for a late assault - in vain - on the Red Bulls.
Raikkonen followed the Ferraris home in fifth place, ahead of the impressive Nico Hulkenberg's Force India and the second Lotus of Romain Grosjean.
Sebastian Vettel on 'perfect' Korean GP win
It was a sobering afternoon for Hamilton, who ran fourth behind Alonso in the early laps after the Ferrari passed him on the main straight on the first lap.
But he began to struggle for grip with high tyre usage caused by a broken rear anti-roll bar - at about lap 18, McLaren said - and was forced to make a third pit stop. He was the only driver in the field who had to do so.
That dropped him to 10th, behind the Toro Rossos of Daniel Ricciardo and Jean-Eric Vergne.
Ricciardo was passed by Vergne in the closing laps, with Hamilton right behind them.
But Hamilton's attempts to pass were hindered by his running wide at Turn 13 and picking up some of the artificial grass, which trailed from his car in the last three laps.
That badly affected his car's rear downforce and he dropped back from the Toro Rossos, only just holding off the Sauber of Sergio Perez for 10th on the final lap.
Hamilton's team-mate Jenson Button retired after being hit by Sauber's Kamui Kobayashi on the first lap.
Korean Grand Prix 2012, day three
Sunday, 14 October: Race replay 14:05 BST; BBC One. Highlights 19:00 BST BBC Three.
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