Justice Ministry officials said Monday that around 600 inmates were taking part in the protest, adding that the government had flatly ruled out considering their demands.
The prisoners have reportedly warned that their families and supporters are also planning protests outside the jail in solidarity.
Draft legislation granting a general amnesty to suspects involved in the 2017 parliament attack by pro-conservative protesters is due to be submitted to the legislature by the end of the week.
The attack left more than 100 people injured, including lawmakers and journalists.
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