Kylian Mbappe struck twice as Monaco claimed a thrilling 3-2 win at Borussia Dortmund in Wednesday's rescheduled Champions League quarter-final first leg to seize the advantage in the tie.
Police ramped up security in the city as German investigators detained an Islamist suspect over three explosions that rocked Dortmund's team bus on Tuesday and left Spain international Marc Bartra with a broken wrist.
Dortmund coach Thomas Tuchel had criticised the decision to go-ahead with the game.
"We would have liked to have had more time to work through it," he said.
"There are players who easily brushed it off, but there are also players who really took it to heart. They are more thoughtful."
Dortmund defiantly vowed not to "give in to terror" after the harrowing events from 24 hours earlier, but the home side struggled early and fell behind on 19 minutes – although only after Fabinho missed a rare penalty.
Mbappe bundled in the opening goal from an offside position before Sven Bender, filling in for Bartra in defence, headed into his own net to compound Dortmund's problems.
Ousmane Dembele pulled one back for Dortmund on 57 minutes, but Mbappe fired in his second of the game to leave Monaco as favourites to reach the last four despite Shinji Kagawa's late strike.
Extra forces were deployed around team hotels and their buses took designated safe routes to the stadium.
Dortmund players wore t-shirts bearing a message of support for Bartra prior to kick-off, while goalkeeper Roman Burki warmed up in the defender's number five jersey.
The 26-year-old was replaced in the line-up by Bender, although Tuchel elected against rushing Marco Reus back into the side having been sidelined since March 4 with a hamstring injury.
Monaco were without midfielder Tiemoue Bakayoko, their last-16 hero against Manchester City, due to suspension, while full-backs Djibril Sidibe (appendicitis) and Benjamin Mendy (groin) were both ruled out.
Pierre-Emerick Aubameyang, scorer of a hat-trick when Dortmund brushed aside Benfica in the previous round, rifled a snap shot just over as the hosts fired an early warning.
But Monaco were awarded a penalty when Mbappe was tugged back by Sokratis Papastathopoulos, only for Brazilian Fabinho – who had converted all 16 previous career spot-kicks – to drag wide of the left-hand post.
Their anguish lasted just two minutes, although there was a huge element of fortune involved as Monaco took the lead through Mbappe.
Bernardo Silva found Thomas Lemar on the edge of the area, with the Frenchman's miscued effort forced in by Mbappe at the far post despite the forward straying offside.
Kagawa then scuffed wide from an inviting low cross from Matthias Ginter, and that miss proved increasingly costly when Bender headed Andrea Raggi's delivery into his own net on 35 minutes.
Tuchel rolled the dice at half-time by introducing American teenager Christian Pulisic and Nuri Sahin in place of the hapless Bender and Schmelzer, and the changes immediately reaped rewards.
Pulisic tormented Raggi on the right wing, but it was a cross from Raphael Guerreiro on the left that led to Dembele reviving Dortmund's hopes.
Aubameyang acrobatically flicked the Portugal international's cross into the path of Kagawa who squared for Dembele to slide into an empty net just before the hour.
Guerreiro drilled a dangerous low ball across the face of goal as Dortmund pressed for an equaliser, while Falcao nearly landed a sucker punch only to blaze over on the stretch after rounding Burki following a superb pass from Lemar.
But Mbappe was less forgiving, intercepting a risky pass from Lukasz Piszczek and sprinting towards the Dortmund goal before finishing superbly past Swiss international Burki.
Kagawa grabbed a lifeline for Dortmund with six minutes left, expertly controlling a Sahin cross and wriggling past Jemerson to slot beyond Monaco goalkeeper Danijel Subasic.
But after ending Dortmund's 32-game unbeaten run at home, Leonardo Jardim's side will be confident of advancing to the semi-finals next Wednesday, although they will be without the suspended Fabinho.