Hopes of a strong challenge to Mercedes' dominance from Ferrari were boosted on Thursday as Sebastian Vettel produced the quickest times of Formula One's pre-season to date, despite seemingly easing off.

Ferrari have been tipped by many to fare well in 2017 - amid a host of regulation changes - and there was certainly plenty to encourage supporters of the Italian team in the latest session of testing in Barcelona.

Vettel set the fastest testing times of the year to date, twice beating the previous benchmark set by Mercedes' Valtteri Bottas.

To add further intrigue, the German's quickest laps featured relatively slow final-sector splits - fuelling suspicion that Ferrari have the capability to go much quicker.

Three-time world champion Lewis Hamilton (+0.328secs) was the only driver within a second of  Vettel's fastest time of one minute and 19.024secs on Thursday.

There was more technical woe for McLaren, however, as Stoffel Vandoorne twice stopped either side of recording his team's best lap of pre-season so far.

Sauber's Marcus Ericsson and Williams' Lance Stroll put the most laps on the board in the morning session, completing 88 and 85 circuits respectively.