Peter Bosz's side continued their outstanding form with a routine 3-0 home win over Cambuur in Arnhem.
Marko Vejinovic gave Vitesse the lead in the 33rd minute, converting an assist from Chelsea loanee Lucas Piazon.
Defender Kelvin Leerdam doubled their advantage five minutes after the break before substitute Giorgi Chanturia – one of three Georgians in the club's matchday squad – sealed the win with an injury-time strike.
Ajax are still two points behind the leaders after strolling to a 4-0 success at lowly ADO Den Haag.
Den Haag are just one point ahead of rock-bottom NEC and were never in their match against an Ajax side who are aiming for their fourth successive title.
Davy Klaassen opened the scoring in the 10th minute and Viktor Fischer also netted before half-time.
Further strikes from Ricardo van Rhijn and Barcelona loanee Bojan Krkic in the second half wrapped up Ajax's success.
Other results on Sunday saw PSV's struggles continue, as they threw away a lead and lost 3-1 at Feyenoord.
Highly rated youngster Adam Maher had given PSV a 21st-minute lead but Jean-Paul Boetius changed the complexion of the match with his goal on the stroke of half-time.
Italian Graziano Pelle then scored a penalty nine minutes into the second half before missing another spot-kick just a few minutes later, after Jeffrey Bruma was sent off.
Pelle atoned for his error with a second in the 65th minute and that was enough for Feyenoord, who sit fourth in the table, six places above PSV.
And NEC won for just the second time this season, as a second-half double from Iran attacker Alireza Jahanbakhsh saw them edge AZ 3-2.
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