Lewis Hamilton threw down the challenge to runaway championship leader Sebastian Vettel by beating the German to the fastest time in both Friday practice sessions in Korea.

A 1:39.63s effort proved enough to put the Mercedes driver ahead at the end of the opening 90 minute session, while the late afternoon saw the pace drop by almost a full second.

Third fastest in Practice 2 for Nico Rosberg proved further encouragement for Mercedes, which has failed to see the podium in each of the last two races.

“I definitely feel like I have a better foundation this weekend,” said Hamilton after practice.

“I’m really happy with the way everything has gone. We have still got some improvements to make but we look like we are competitive.”

Fourth for Mark Webber made for a Mercedes/Red Bull lock-out of the top spots, while the Ferrari (Felipe Massa fifth, Fernando Alonso seventh) and Lotus (Romain Grosjean sixth, Kimi Raikkonen eighth) drivers completed the top eight.

Raikkonen’s car had been the subject of a significant repair effort between sessions following a heavy crash at the final corner late in Practice 1.

The Finn, who entered the weekend under a back injury cloud following complaints at the Singapore Grand Prix two weeks ago, emerged from the incident unscathed.

See below for the full Practice 2 result

See below for the full Practice 1 result