U.S. Secretary of State John Kerry expressed "grave concern" to his Russian counterpart on Thursday over a sharp rise in separatist attacks in eastern Ukraine and urged an immediate ceasefire, Reuters cited State Department as saying. Kerry's comments, in a telephone call with Russian Foreign Minister Sergei Lavrov, reflected growing U.S. worries about the increasing violence between Ukrainian government forces and pro-Russian rebels. -- SPA 22:06 LOCAL TIME 19:06 GMT تغريد