Demonstrations sparked by a U.S.-made video resumed in Egypt and spread to Yemen, Iraq and Iran on Thursday, September 13, leaving four protesters dead and threatening to escalate further in the Muslim world on Friday, the region’s customary day for prayer and protest, The Wall Street Journal reported. Two days after armed attackers killed the ambassador and three other Americans at the U.S. Consulate in Benghazi, Libya, hundreds of young men breached some outer layers of security surrounding the U.S. Embassy in Yemen’s capital. In Cairo, hundreds of Egyptian police beat back crowds of young men outside the U.S. Embassy, injuring 16 people. While the protests were initially triggered by a video seen as insulting to the Muslim Prophet Muhammad, there were indications on Thursday that many protesters were using the unrest to put pressure on their own countries’ fledgling governments.