Thirty-one people were killed Monday in clashes in Yemen, 28 in Sanaa, and three in Taiz, according to medical officials.  On Sunday, at least 26 protesters were killed and more than 550 were wounded -- hundreds of them by gunshots -- when security forces fired live bullets and tear gas at a massive demonstration in the city, a medic said. The death toll was expected to rise because some were in critical condition, witnesses said.  "The situation is getting very tense," said a resident of downtown Sanaa who asked not to be named for safety reasons. "We can hear gunshots, explosions, RPGs (rocket-propelled grenades) constantly."  "This now seems more like a military fight, and we're really worried this could become a civil war. We're really worried it could spread all over," the resident said.  The U.S. Embassy in Yemen issued a statement saying the United States "regrets the deaths and injuries of many people" in the protests Sunday. "In this tense situation, we call upon all parties to exercise restraint. In particular, we call on the parties to refrain from actions that provoke further violence."  The U.S. government remains hopeful for a peaceful transition, the statement said.  U.N. Secretary-General Ban Ki-moon's office said he is "gravely concerned" and "calls on all sides to exercise utmost restraint and desist from provocative actions. He strongly condemns the excessive use of force by government security forces against unarmed protestors in the capital Sanaa, resulting in scores of people killed and many more injured."  "Yemen is on a knife edge," Philip Luther, Amnesty International's deputy director for the Middle East and North Africa, said in a statement issued Monday.
A violent crackdown by Yemeni authorities has left dozens dead at protests, witnesses and medical officials said Monday.Bloody violence raged Monday in the capital, Sanaa, triggering a new wave of