A school was hit in a government airstrike on Wednesday in the opposition-held district of Aleppo, killing at least 19 people, including 10 children, activists reported.
The attack hit the Ein Jalout school in the eastern part of Aleppo as teachers and students were preparing an exhibit of children’s drawings depicting the war, activists said.
In an activist video, the bodies of the 10 children were laid on the ground of a local hospital wrapped in sheets.
The killings come just days after a report from Human Rights Watch saying that both regime and rebel forces had ignored a February condemnation by the United Nations of strikes targeting or hitting civilian areas, with hundreds perishing since then.
Activist videos of the scene showed bulldozers removing rubble from the smashed building. They also showed some of the children's drawings and paintings. One child’s picture showed a hanging skeleton surrounded by skulls with a child nearby being shot by a gunman in a ditch.
The child has a speech bubble written above her head in broken English that partly reads: "Syria will still free."
The Britain-based Syrian Observatory for Human Rights, a group opposed to President Bashar al-Assad, said at least 19 people were killed in the strike.
The United Nations children’s agency, UNICEF, said in it was “outraged by the latest wave of indiscriminate attacks perpetrated against schools and other civilian targets across Syria.”
Thousands of Syrian children have died in Syria's three-year-old conflict, which began as an uprising against Assad's rule, but has now become a civil war that has left more than 150,000 people dead and displaced millions.
Aleppo, Syria’s largest city, has continued to bear a large brunt of the violence from the ongoing civil war being divided between government forces and opposition groups for nearly two years.
Forces loyal to Assad have been carrying out airstrikes and dropping crude barrel bombs in rebel-held districts in the eastern part of the city, at times hitting schools, mosques and markets.
The latest attack comes after a mortar attack and dual car bombing on Wednesday killed at least 54 civilians in the pro-Assad districts in Homs and Damascus.
The ongoing violence continued as Assad announced earlier this week that he would run for re-election. In a televised campaign-style appearance on Tuesday, Assad and his wife Asma met with parents who had lost their only sons in the conflict.
Meanwhile, the United Nations said that a Security Council measure designed to provide aid to millions of Syrians was not working.
Less than 10 percent of the 242,000 people living in besieged areas received assistance within the past four weeks.
"The humanitarian situation in Syria is beyond catastrophic. More than two months after a U.N. resolution to alleviate the suffering of civilians and end war crimes was adopted, the situation there has only worsened," said Jose Luis Diaz, from the U.N. office in New York.
The 15-member panel is in deadlock. Western powers would like to refer Syria to the International Criminal Court (ICC) or introduce targeted sanctions against those violating the resolution. Russia, which maintains long-held military and political relationship with Damascus, has pushed against sanctions.
Al Jazeera and The Associated Press