Italy striker Mario Balotelli fired Nice ahead with a close-range finish after a darting run by midfielder Jean Michael Serri in the 32nd minute.
But Ajax, last season's second-tier Europa League runners-up, levelled after poor defending allowed midfielder Donny van de Beek to sweep the ball home from 10 metres.
Celtic's hopes were left hanging in the balance after a tepid display against the Norwegian champions, who should have taken away more into the return leg as Yann-Erik de Lanlay squandered a gilt-edged chance on the hour.
The forward blazed his shot from 10 metres over the bar with only goalkeeper Craig Gordon to beat but Celtic could not take advantage in the closing stages.
Istanbul Basaksehir, making their first Champions League appearance, almost staged the shock of the night after fighting back from a two-goal deficit in a thrilling 3-3 draw at Club Bruges.
The home side looked in cruise control after scoring twice in the opening 16 minutes but were stunned as Marcio Mossoro netted a brace and Eljero Elia added another to turn the match on its head.
Stefano Denswil spared Bruges's blushes but they still face a difficult task in the return leg.
Patrick Twumasi struck in the 90th minute to delight Astana fans after Armando Sadiku had pulled one back for Legia, who trailed 2-0 at halftime.
There was also late drama and two stoppage-time goals in Kiev, where Dynamo's Denis Garmash had the final say after Christian Fassnacht scored what looked like a vital away goal for Young Boys.
Andriy Yarmolenko and Dieumerci Mbokani had given Dynamo a 2-0 first-half lead in the Olimpiyskyi stadium, the venue of next year's Champions League final.
Croatian champions Rijeka, seeking their maiden group stage appearance, held on for a 1-1 draw at Salzburg after the home side's Korean forward Hee-Chan Hwang cancelled out a glancing header by Mario Gavranovic.
(Writing by Zoran Milosavljevic; Editing by Toby Davis)
Share
