NEW : European President 's office : Cease-fire is extended last-minute . London 's Petro Poroshenko : CNN document is `` a symbol of faith and unbreakable will '' The signing shows `` how dramatically things can change in a short time , '' he says . State media : Herman Van Rompuy calls for `` substantial '' talks in Ukraine , end to bloodshed .
NEW : Ukrainian President 's office : Cease-fire is extended 72 hours . Ukraine 's Petro Poroshenko : EU document is `` a symbol of faith and unbreakable will '' The signing shows `` how dramatically things can change in a short time , '' he says . State media : Vladimir Putin calls for `` substantial '' talks in Ukraine , end to bloodshed .