Daniel Ricciardo was the beneficiary of a loose headrest for Lewis Hamilton as tensions between the Briton and Formula One title rival Sebastian Vettel threatened to boil over in an enthralling, incident-packed Azerbaijan Grand Prix.

Mercedes driver Hamilton, who won in Canada last time out and started on pole, was seemingly on course to pick up a comfortable victory and make further inroads into Vettel's championship advantage after maintaining his lead following a red flag.

Vettel was also hit with a 10-second penalty for deliberately shunting Hamilton when coming into the pits following that flag on lap 22 after several collisions saw the track littered with debris, with the Ferrari man fuming when he felt Hamilton had deliberately slowed down under the safety car, causing contact between the two.

But luck was not on Hamilton's side when his protective head rest came loose and he was forced to pit.

Vettel emerged from his penalty just ahead of Hamilton, and the German fought his way back up to fourth to finish one place in front of his rival in the race of the season and stretch his lead to 14 points.

Ricciardo ultimately went on to claim a surprise victory, the Australian having completed a brilliant move on Williams duo Felipe Massa and Lance Stroll following the red flag.

Valtteri Bottas was involved in a second-corner collision with Kimi Raikkonen on lap one, but fought back from dead last to pip Stroll to second on the line and limit the damage for Mercedes – Stroll having the consolation of a maiden podium finish.