The rights organization said it was able to document a number of cases where teenage boys were detained by security forces for allegedly attacking police officers or for taking part in anti-government protests. It said others were detained "without cause."
"The Bahraini authorities need to look into these allegations and immediately call a halt to any arbitrary arrests and mistreatment of children," Joe Stork, acting Middle East and North Africa director at Human Rights Watch, said in a statement Sunday from Beirut.
The British government has issued series of routine travel advisories warning weekly protests in Bahrain could turn violent.
Dozens of people were killed during 2011 demonstrations. Bahrain says it's committed to recommendations outlined by a panel probing the government's response to the unrest. Reformers say protests are ongoing.
The European Parliament passed a resolution last week calling on authorities in Bahrain to address the human rights situation. It also calls on the government to treat juvenile detainees according to international norms.
The official Bahrain News Agency reported Sunday three defendants were sentenced to 10 years in prison for the premeditated murder of members of the security force. It didn't indicate the age of the defendants.