Bayern Munich's hopes of progressing to the knock-out phase of the Champions League suffered a mauling in Minsk on Tuesday as they slumped to a shock 3-1 defeat at Belarus champions BATE Borisov.
"This is a sensational result for us, we will celebrate a bit but we need to keep working hard," said BATE's ex-Arsenal star Aleksandr Hleb.
"Bayern are still favourites in our group, we are taking it one match at a time.
"It was a very difficult match but we fought until the end."
With the Group F match held at Dinamo Stadium in Minsk, Bayern's defence leaked goals either side of half-time as midfielder Aleksandr Pavlov, then striker Vitali Rodionov put BATE on the way to their second straight European win.
France wing Franck Ribery pulled back a late consolation in the 91st minute, but a brilliant Renan Bressan goal from a counter-attack, 10 minutes after he came off the bench, left Bayern well beaten.
"I already knew before the game then we would be facing a very good opponent and you have to take your chances to go ahead," said Bayern coach Jupp Heynckes after midfielder Toni Kroos hit the post early on.
"We had them under permanent pressure, but we have to accept our opponents' victory."
Having won 3-1 at Lille in France a fortnight ago, victory in Minsk leaves BATE top of Group F while Bayern failed to back up their opening 2-1 home win over Valencia, scoring one goal despite 20 shots on goal and 43 crosses.
This was Bayern's first competitive match against a side from Belarus, but it proved to be a long flight back to Munich for last season's beaten Champions League finalists as the hosts claimed a deserved win.
With Arjen Robben left back in Munich to recover from a thigh injury, Kroos squandered a great chance to put Bayern ahead when he rounded BATE goalkeeper Andrei Gorbunov, but his shot hit the post on 13 minutes.
After a clever pass from right-back Denis Polyakov in the build-up play, BATE'S Pavlov gave Bayern goalkeeper Manuel Neuer no chance with a low shot to put the hosts ahead on 23 minutes.
Despite enjoying only 40 percent possession, the hosts were only denied doubling their lead by some fine work from Bayern goalkeeper Manuel Neuer.
A crisp exchange of passes between Rodionov and ex-Arsenal midfielder Aleksandr Hleb opened up some space and after Hleb's clever backheel, Polyakov's fierce shot was brilliantly saved by Neuer on 55 minutes.
BATE kept attacking in waves and when Pavlov found himself in space in the penalty area, he could only fire over with the goal at his mercy with 35 minutes left.
Despite the lion's share of possession, Bayern looked no closer to breaking the Borisov defence with coach Jupp Heynckes throwing on striker Claudio Pizarro and misfielder Bastian Schweinsteiger.
Munich were finally floored when Rodionov exchanged passes with midfielder Edgar Olekhnovich which put the striker clear and he brushed off both Bayern defenders Jerome Boateng and Dante to fire home on 78 minutes.
A superb through pass from Bayern's Swiss midfielder Xherdan Shaqiri, who was fresh off the bench, was drilled home by Ribery in added time to give the guests hope.
However, with the Bayern defence all at sea, subsitute Dmitri Mozolevsky sprinted clear and passed to fellow replacement Bressan in the 94th minute to compound Bayern's misery.