Fellow rights activist Raisa Mikhaylovskaya told RFE/RL that police arrested Vouchak on May 24 when he was outside his office in Minsk talking with a colleague.
The colleague, Zmitser Kukhley, said he did not hear Vouchak use any vulgar words in the presence of the police officers.
Vouchak was found guilty and sentenced later on May 24.
Vouchak is a former investigator at the Minsk prosecutor's office.
Since 1990, he has been involved in human rights activities.
In January, he was found guilty of verbally insulting police and sentenced to four days in jail.
Vouchak’s colleagues say his arrest is politically motivated.
-- RFE/RL’s Belarus Service