He says a total of 158 men in their 20s and 30s were arrested during riots that began on Tuesday that left one person dead and 75 others, including 58 policemen, injured.
While 30 have been released for lack of evidence, the remaining 39 are still being questioned, he says. The 89 who have been charged face up to 15 years in jail.
Protests across the country—featuring rare calls for the overthrow of the king—turned unusually violent last week.
The official, who spoke on Sunday, insisted on anonymity as he was not authorized to speak about the case.