"This is a tragedy that, as is with all such tragedies, is incomprehensible and inconsolable," ruling National Conference spokesman J A Mattu said in a statement.
"We demand a thorough probe into the circumstances leading to the death of the youth and also demand that responsibility be fixed," he said.
Opposition Peoples Democratic Party (PDP) also condemned the death of 15-year-old Suhail Ahmad Mir.
PDP president Mehbooba Mufti expressed sympathy with the bereaved family and prayed for peace for the deceased.
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Mehbooba said the government must also deal with the situation with care.
CPI(M) state secretary M Y Tarigami, while condemning the killing, said the culprits must be identified without delay and brought to justice.
Expressing condolences, Tarigami alleged that the administration deals with every situation either by imposing curfew or through the use of excessive force against people.
The CPI (M) leader demanded a time-bound judicial probe into the incident to fix responsibility and punish the culprits to send a message that no one is above the law.
Mir was killed in alleged CRPF firing during protests against Israeli aggression in Gaza Strip.