Barcelona ace Lionel Messi has warned fans their Champions League semifinal is not over.

Messi struck twice in the 3-0 first-leg win over Bayern Munich.

"We earned a good result, but we've not yet won anything," he posted on Facebook.

"There is still 90 minutes in Munich which will be very difficult. We must be prepared.

"Bayern have good players and will recover those who were injured. The reality is that they are going to attack from the start and with the support of all their fans."