Over 3,000 people, according to milinkevich.org, gathered to cheer for their leader at Liberty Square. However, many people were not able to get to the venue, as access to it was blocked by law enforcement.
Today many Belarusian websites encountered problems, either technical inability to welcome so many visitors or were these DoS attacks, but just out of my own browsing experience (from US), I had troubles accessing Milinkevich.org, kozylin.com, charter97.org, and RFE\RL (svaboda.org).