A powerful blast ripped through a pickup truck in the south Syria province of Daraa early Wednesday, killing 21 people including four children, a monitoring group said. \"Twenty-one people were killed in the Nawa area (of Daraa), among them four children and six women, in a blast that detonated as their vehicle went past Tal al-Jumua,\" where a battalion of troops loyal to President Bashar al-Assad is positioned, said the Syrian Observatory for Human Rights.