Maxwell Dlamini, Swaziland's best known student leader, was arrested by police and detained for four hours after allegations that he did not stick to bail conditions.
Pro-democracy supporters are saying Dlamini is being harassed by police.
Dlamini faces charges that he was in posession of explosives in April 2011. He had spent nearly 10 months in jail on remand before being released on bail in February 2012, after an international campaign.
Dlamini denies the charges and says he was tortured by police into making a confession.
Dlamini's rearrest sparked anger among supporters. The Swaziland Youth League (SWAYOCO), writing on Facebook called it 'disgusting'.
Dlamini told readers of Facebook, the police had told him he had not been keeping to the conditions of his bail, which included reporting to Mbabane Police station three times a week.
Dlamini, who is president of the Swaziland National Union of Students, said he had kept to all bail conditions, but the police were so inefficient they had failed to keep proper records of his visits.
'It has always been the state which has failed to keep proper records and their inefficiencies on their part that I was not captured on the records book at times.
'This was because either the record book was missing or the office responsible was absent from work,' he wrote.