Manchester United face a tough Champions League encounter after they were drawn against Real Madrid in the first knockout round of the competition.

The former Premier League champions were arguably hoping to avoid the Spanish giants but Sir Alex Ferguson's men will have to travel to the Bernabeu for the first leg, which will take place on February 12 or 13.

The tie means that Portuguese star Cristiano Ronaldo will return to his former club, while Madrid boss Jose Mourinho, who has been touted as a possible future successor to Ferguson, will also be under the spotlight for the return leg at Old Trafford.

Meanwhile, Arsenal, who could have met Barcelona in the knockout rounds, were drawn Bayern Munich, who succumbed to defeat in last year's final against Chelsea in a penalty shootout.

Scottish Premier League champions Celtic will need to overcome Italian giants Juventus over two legs in order to reach the quarter-final stage of the competition.

Round of 16 draw in full:

Galatasaray vs. Schalke
Celtic vs. Juventus
Arsenal vs. Bayern Munich
Shakhtar Donetsk vs. Borussia Dortmund
AC Milan vs. Barcelona
Real Madrid vs. Manchester United
Valencia vs. Paris Saint-Germain
Porto vs. Malaga