No group has claimed responsibility for the attack, which appears to be one of the first cases in which Iraqi insurgents have used a young boy to carry out such a suicide mission.
The reports have shocked observers in many parts of the world, including mainstream Muslim clerics.
Several Islamic scholars interviewed by RFE/RL said Islam condemns the use of children for military purposes.
Khodaiverdi Egamberdi, head of FATWA at the Islamic Center of Tajikistan, said suicide is un-Islamic and those who force children into suicide bombings cannot be considered Muslims.
"These are not Islamic acts; Islam does not allow a person to kill himself," Egamberdi said. "These are terrorist acts. Maybe they promised something to that child and his parents, [but] Islam doesn't accept it."
Muhammad Sodiq Muhammad Yusuf, a prominent religious scholar in Tashkent, said suicide bombings by civilians -- including women and children -- are forbidden by Islam.
"Involvement of children in this is not supported by Shari'a [Islamic law]," he said. "Involving children whose development is not fully completed yet, cannot be supported from a religious point of view, nor can it be understood from a human point of view."
Kyrgyz Mufti Murataaly Hajji Jumanov said the use of children as human bombs is considered a grave sin in Islam.
"Our prophet [singled out those who misused children] saying, 'They are not from us, they are not from my community,'" Jumanov said. "There is such a hadith that says that someone who does not treat children with kindness and who does not respect people older himself, that man is not from our [Muslim] community."
The head of the Crimean Tatar Mejlis, the top body representing the Crimean Tatar community on Ukraine's Crimea peninsula, and member of the Ukrainian parliament, Mustafa Djemilev, said those who recruit children for terrorist purposes commit a serious crime and should be held responsible.
"It is clear that those who packed the child with explosives were adult men," Djemilev said. "And the biggest sin is of course on those adults. I simply cannot find words -- it's a loathsome crime to involve children in such blasts."
Farid Mohammad Omar, the imam of one of Kabul's mosques, also condemned the misuse and manipulation of children by terrorist groups.
"They cause incitement, they push [children] in this direction; instead there should be peaceful incitement, children should be [brought up] in a way so that they can offer something for the future of the society," Omar said. "But if you tell them go and kill, it is like the pre-Islam era when girls were buried alive. Today, children should be given a good, Islamic education. In my view, what they do is wrong; it causes death and it gives Islam a bad name."
In recent years, there have been several cases of the use of children and teenagers as suicide bombers in the Middle East conflict.
During the 1980-88 Iran-Iraq War, young Iranian boys were used as soldiers on a large scale. Mohammad Hossein Fahmideh, a 13-year-old member of the volunteer Basij forces who blew himself up to destroy an Iraqi tank on the battlefront, is glorified in the Islamic Republic of Iran as one of the heroic symbols of the war.
UNICEF spokesman in Geneva Damien Personnaz told RFE/RL that the use of children in military conflict should be strongly condemned.
"UNICEF is quite concerned about this very sad event," Personnaz said. "I think we should always remind that all parties should never use children for any kind of issues related to war, or to bombings, or to suicide attacks."
Reports have suggested that Iraqi insurgents placed bombs on a mentally impaired boy during the country's January legislative elections; the explosives on the boy detonated near a polling station, killing him and at least one police man who ushered him outside.
The use of individuals under the age of 18 in armed conflicts is prohibited by the optional protocol of the UN Convention on the Rights of the Child. UN Security Council Resolution 1261 describes the use of children as soldiers as a "violation of international law."
Personnaz said children are vulnerable to military recruitment because of their immaturity.
"Definitely I don't see children being very much attracted to these kind of things unless they are being brainwashed or specifically trained for it," Personnaz said. "I'm not that sure yet this is a trend, because it is much too early to say."
Human rights groups say children can also be driven to join armed forces and militant groups because of poverty or discrimination.
It is estimated that there are currently 300,000 child soldiers involved in conflicts around the world. UNICEF says they are being robbed of their childhood.
(RFE/RL's Tajik, Uzbek, Tatar Bashkir, Ukrainian, Afghan and Kyrgyz services contributed to this report.)