BNA, Bahrain's official news agency, said on Friday: "Eighty people gathered in the Sanabis district on Thursday night trying to organise a street gathering.
"After they were told to disperse because this is illegal, they began throwing stones and Molotov cocktails at security forces."
It said the 15 people arrested were between 13 and 15 years old and would be transferred to state prosecutors.
Aljazeera satellite channel showed scenes of police in riot gear using teargas on protesters on Thursday in what it said was the third night of clashes in the capital, Manama.
Claims of abuse
The clashes followed claims by a 24-year-old Bahraini that he had been beaten and sexually abused by masked men.
The man, part of a group called "The Unemployed Committee", said in a statement that his attackers warned him to stop organising protests, which had been peaceful, earlier in the week over the job situation.
The least wealthy of the Gulf Arab oil producers, the island state of Bahrain has a history of political tension.
At least 15 protesters were injured in clashes with police during a demonstration in July.
The Labour Ministry announced a 30-million-dinar ($80 million) training programme earlier this year to help find jobs for Bahrainis.
Independent economists put unemployment at around 15%.