Monaco scored an 89th-minute equaliser from the penalty spot to come from 2-0 down and deny Dinamo Zagreb in torrential conditions in Croatia.
Zagreb, who had been thrashed 9-2 by Bayern Munich in their last Champions League outing, opened the scoring through Petar Sucic on the break on the stroke of half-time.
In heavy rain which affected both sides' performance, Zagreb added a second through midfielder Martin Baturina's superb curling effort in the 66th minute.
But Monaco, who beat 10-man Barcelona 2-1 last month, halved the deficit through Mohammed Salisu's 74th-minute header.
And, moments after ex-Liverpool winger Takumi Minamino had an effort cleared off the line, Monaco were awarded a penalty after a foul on Folarin Balogun.
Captain Denis Zakaria blasted the spot-kick into the net with one minute of normal time remaining.
By conceding two goals, Dinamo broke the record for most goals conceded in their first two Champions League matches of a single campaign.
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