Ajax have sealed their 35th Dutch League, Eredivisie title after a comfortable 4-0 victory over Emmen.
Jurrien Timber’s strike in the 10th minute gave Ajax the lead in the first half.
Sebastien Haller at the hour mark doubled their lead, while Devyne Rensch scored the third goal.
In the 74th minute, Tadic crossed for Klaassen headed in a fourth, and Ajax then comfortably saw out the rest of the game to seal the league championship.
According to Dutch news agency ANP, thousands of fans gathered around the stadium despite calls from the authorities to avoid gatherings.
Although Ajax was leading the table last season, it was, however, halted in early March by the Covid-19 pandemic and no champion was crowned.
— AFC Ajax (@AFCAjax) May 2, 2021
On Friday, Ajax announced the extension of the contract of coach Erik Ten Hag till 2023, ending rumours of his exit to Borussia Dortmund in the Bundesliga or Tottenham in the Premier League.