Lewis Hamilton, Sebastian Vettel clash under Safety Car in Baku

BAKU, Azerbaijan -- Title rivals Lewis Hamilton and Sebastian Vettel made contact behind the Safety Car at the Azerbaijan Grand Prix in what could prove to be a major flashpoint in the year's championship battle.

A dramatic first half of the race saw three Saftey Car periods in quick succession and it was on the second of these that the contact between the championship leaders happened. As the cars prepared for the restart, Hamilton, who was leading the field, started to bunch the cars behind him and on the exit of Turn 15 Vettel, in second place, clouted the rear of the Mercedes.

Data from Hamilton's car showed he was on the brakes ahead of the corner and just as he exited, while Vettel got on the throttle as he exited the corner. Parts of Vettel's front wing flew into the air and the Ferrari driver immediately opened his radio channel to accuse Hamilton of "brake testing" him.

As the red mist descended on the Ferrari cockpit, the four-time world champion moved alongside Hamilton -- waving his right hand in the air -- before turning across on the Mercedes and making further contact. With no time to digest what had just happened, Hamilton had to continue with the restart as normal and led the pack away while Vettel was left to fend off the two Force Indias and Felipe Massa. The race was suspended soon after to clear debris for a collision between the Force Indias and the stewards confirmed the Hamilton/Vettel collision was being investigated.

The rules surrounding a Safety Car restart are as follows: "The first car in line behind the safety car may dictate the pace and, if necessary, fall more than ten car lengths behind it.

"In order to avoid the likelihood of accidents before the safety car returns to the pits, from the point at which the lights on the car are turned out drivers must proceed at a pace which involves no erratic acceleration or braking nor any other manoeuvre which is likely to endanger other drivers or impede the restart."

The stewards later issued Vettel a 10-second stop-go penalty for the incident, meaning the championship leader had to pit and remain stationary in the box.

Hamilton later said over the radio: ""A ten-second penalty isn't enough for behaviour like that, you know that Charlie [Whiting]."