Atalanta led 2-0 through Alejandro Gomez and Mario Pasalic goals, both assisted by Josip Ilicic.

Federico Chiesa ran from his own half before rifling home for the hosts and Marco Benassi volleyed a leveller.

Marten de Roon blasted Atalanta back into the lead from 20 yards, but Luis Muriel turned Chiesa's cross home for an equaliser.

It was the second time Fiorentina had come back from two goals down to draw 3-3 in four days, having held Inter Milan on Sunday in Serie A.

Atalanta's only cup win came in 1963, with Chiesa's father Enrico playing in Fiorentina's last success in 2001.

The winner of the second leg will face either Lazio or AC Milan, who drew 0-0 on Tuesday, in the final.

However, the return legs of the two ties are not until Wednesday, 24 April.