Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: (CNN) Peace in eastern Ukraine remains tenuous as a spate of violations of a newly implemented ceasefire continued into Wednesday. A day after the head of the Organization for Security and Co-operation in Europe (OSCE) warned the ceasefire had failed, German Foreign Minister Sigmar Gabriel urged Kiev and Moscow to hold fast to the agreement. Despite assurances given by both parties, he said, the "ceasefire is not holding." "We can only urgently appeal to both sides to implement the agreements we have reached -- otherwise, we will risk an intensified military escalation with many other civilian victims and a continuation of the standstill in the political process," Gabriel said in a statement.Ukraine: "Russia resorts to political and military provocations" rather than full Minsk implementationHeavy weapons still in place; hundreds of violations recorded 
 Question:"The crisis in and around the Ukraine continues to be a major source of tension and instability in _," he said.

Europe