Three defendants were sentenced to 10 years in prison, and two others were jailed for three years over the attack on Dar al-Hukumah, the source said. Two others were acquitted.
Prosecutors accused the group of "attempting to kill security men by throwing petrol bombs at them," according to the list of charges.
They were also accused of "taking part in an illegal assembly of more than five people to disturb security."
The compound is the former headquarters of the government but it is now used by the foreign ministry as administrative offices.
Pictures posted on Twitter microblogging site at the time showed masked men throwing petrol bombs at the complex in the center of the capital.
Lawyers said that the defendants, whose ages ranged between 15 and 33, denied the charges and said they were subjected to torture in detention.
This is while Human Rights Watch (HRW) said earlier on Tuesday that Bahraini security forces regularly “detain children” with no reason and subject them to “ill-treatment” that may amount to torture.
The rights organization said in a report that information received from victims, family members and local human rights activists showed children are often being held in detention for long periods and subjected to beatings and threats of torture, like adult detainees.
The Bahrain Youth Society for Human Rights says it has recorded 22 incidents in which children were detained since August 21.
NJF/NJF