Artemivsk (Ukraine) (AFP) - The UN Security Council scheduled an emergency session to discuss the fragile ceasefire in Ukraine on Friday, a year to the day since Russian troops and pro-Moscow forces began seizing ports and cities on the Black Sea peninsula of Crimea.The anniversary of the seizure, which triggered the worst standoff in East-West relations since the Cold War, came as the shaky ceasefire between Ukrainian forces and pro-Russian rebels appeared to be holding.Ukraine's military said Thursday it had started withdrawing heavy weapons from the front line, bolstering a peace plan that was meant to come into force on February 15 but only took hold across the conflict zone in recent days.The announced pull-back is a key part of a peace deal negotiated earlier this month in the Belarus capital Minsk."Ukraine is today (Thursday) beginning the withdrawal of 100mm cannons from the frontline," the army said in a statement."This is the first step in the pull-back of heavy weapons and will be carried out exclusively under the supervision and verification of the OSCE (the Organization for Security and Cooperation in Europe)."US State Department spokeswoman Jen Psaki said that while there had been a reduction in fighting in recent days, the truce was still being broken."There are still violations...