At least some of the victims died as rescuers struggled to reach a child care center at the Villaggio mall in the capital Doha, according to Qatar's Minister of State for Interior Affairs, Sheik Abdullah bin Nasser Al Thani.
Four of the children killed were Spanish citizens living in the small Arab emirate, the Spanish Foreign Ministry said.
It did not identify the children, citing Spanish privacy regulations. Also, a 3-year-old French child was among the victims, the deputy minister for overseas French citizens, Yamina Benguigui, said in a statement.
"We tried our best, but when we got there, the children were trapped inside. We are very sorry for what happened. We tried as much as we could to save these people," Sheik Abdullah told reporters in Doha.
Four teachers and two civil defense officials were among the dead, the Qatari ministry said on its official Twitter page.
Another 17 people were injured, including four children, according to authorities. Most of those hurt were rescuers responding to the blaze.
Witnesses earlier reported thick black smoke pouring from the ritzy mall around midday. Amateur photos and videos posted online showed firefighters rescuing victims by climbing on the roof.