The 20-year-old fired in the hosts' opener shortly before the break and sealed the points with a fine turn-and-strike 15 minutes from the end, taking his tally to four goals from the season's opening three matches.

Jonathan Bamba had added the second from the spot six minutes earlier after being upended by Mathieu Debuchy.

Lille sit on six points after their second straight home win, level with five clubs including champions Paris Saint-Germain.

Saint-Etienne, who drop down to 13th after their first defeat of the new campaign, were left to rue a penalty award being chalked off by VAR in the 80th minute, with footage showing that Jonathan Ikone had touched the ball with his shoulder rather than his arm.