Syrian forces have fired mortar shells into a farming village, killing 10 people, among them two young children, and sending panicked residents running for cover, activists said. U.N. peacekeeping chief Herve Ladsous deplored the ongoing violence and promised to put 300 observers in Syria by the end of the month, up from the 24 in place now, in hopes of calming the situation, according to a report of the Associated Press. "The level of violence in Syria has been appalling," Ladsous said. Tuesday's attack on the village of Mishmeshan highlighted the vulnerability of Syrian civilians, especially children. Nine of the dead in the village attacked were from one extended family, and many of a dozen wounded were children, activists said. Five mortar shells hit the village at around 1 a.m. Tuesday, and after daybreak, survivors wrapped some of the dead in blankets and placed them in the backs of three white pickup trucks. Amateur video showed hundreds of mourners lining a street next to the parked trucks and praying over the bodies ahead of the burial. In all, 15 Syrian civilians were killed on Tuesday, according to the Britain-based Syrian Observatory for Human Rights, an activist group. A senior U.N. official, Radhika Coomaraswamy, expressed alarm over "yet another wave of extreme violence killing and injuring children across Syria," referring to the mortar attack and other recent violence. She said more than 34 children were allegedly killed since an April 12 truce deadline. The U.N. says more than 9,000 people have been killed since the uprising against President Bashar Assad erupted more than 13 months ago.