Parents have been advised to prevent children from being outdoors until sunset
Judge Mohitul Hoque Inam Chowdhury of the Women and Children Repression Prevention Tribunal delivered the verdict on Wednesday.
The convicts are Dakhshin Surma natives Md Ismail Ali, 22, and Md Mithun Mia, 20, Bharthokhola native Biplop alias Bipul, 18, and Lakshipur District's Junaid Hossain, 19. They are all being held at the Sylhet Central Jail.
His family alleged that the perprators killed Nayeem over an old feud with his family.
A case was started by Nayeem's father Abdul Hoque as plaintiff against several unidentified suspects with Dakshin Surma police on Aug 20, 2011. On Nov 26 that year, Dakshin Surma Police Deputy Inspector Md Harun Mazumber formally pressed charges against five suspects in the case.