Forces loyal to President Salva Kiir and Vice-President Riek Machar had battled each other with anti-aircraft guns, helicopters and tanks since Thursday - almost five years to the day after South Sudan declared independence from Sudan.The violence has raised fears of a collapse of a nearly year-old peace deal that was supposed to end two years of ethnically charged civil war between Kiir and Machar's supporters.Both leaders deny responsibility for starting the violence.A ceasefire called on Monday appeared to hold and officials from Machar's side said he was ready for talks. But there were no details of a meeting or an accord...