Syrian forces have killed at least four protesters and arrested scores of others on the eve of another mass protest against President Bashar al-Assad. A convoy of tanks and armed forces reportedly attacked a crowd gathered in a central square in the city of Deir ez-Zor. The human rights group, Avaaz, says it’s identified nearly 3,000 people who have gone missing after being seized by Assad’s troops, an average of one person per hour during the four-month uprising. Syrian activists say up to 1,600 people have been killed during the crackdown.