Deputy Attorney General Mohammed Salah said public prosecutors Monday started investigations into Friday protests in Manama.
"The public prosecution has interrogated 28 suspects in the presence of their attorneys and ordered their precautionary incarceration for interrogation purposes," the official Bahrain News Agency reported.
The agency adds about 100 demonstrators blocked traffic in Manama and resisted the efforts of law enforcement officials to restore order.
Bahrain was praised recently for a decision to reach out to members of the opposition for a national dialogue. The country's human rights record has been called into question as it responds to a simmering protest against the ruling Sunni monarchy.
A member of the opposition al-Wefaq party told the BBC that it would continue its campaign of civil disobedience.
"Agreeing to dialogue doesn't mean that we stop our protests," an unnamed spokesman for the opposition party said.
Bahrain says it's committed to a reform initiative outlined by an independent panel probing a government crackdown on 2011 demonstrations.