The nine were among about 24 people taking part in a rare public demonstration in Rangoon last Thursday.
A new activist group calling itself 88 Generation Students says the protesters were peaceful and should have been allowed to express their sentiments, needs and suffering.
The opposition National League for Democracy condemned the arrests. Military-ruled Burma has little tolerance for political dissent and restricts freedom of assembly and the media.
Burma's military regime holds at least 1,100 political prisoners. The head of the National League for Democracy, Aung San Suu Kyi, has spent most of the past 17 years under house arrest.
The 88 Generation Students is made up of participants in a pro-democracy movement in 1988. Burma's military leaders crushed that movement.
Information for this report is provided by Reuters and AP