In the years before 1914 violent pogroms were directed against Jews, who were made scapegoats for the problems of the Russian Empire. The flight of Jews from the east, first to escape the violent prejudices unleashed periodically in Tsarist Russia and then to escape the upheavals in the aftermath of World War I, sharpened the anti-Semitism which was already to be found in the west of Europe [Source]
I am looking for a source to support the statements above.
Also, what else is considered to have played a role in the growth of international anti-semitism that was a precursor to the persecution of Jews by NS Germany?
The rise really started in 19th century. The main reason was the general rise of nationalism related to creation of nation-states in Europe. Shortly before that, or simultaneously, the Jews were emancipated in most European countries. They left the ghettos, where they lived in relative isolation and started to mix with general population. With growing nationalism, this led to antisemitism.
In 1914 these processes were accelerated by the World war.
EDIT. The Russian empire is a special case: it was never a nation-state, and Jews did not obtain equal rights until 1917. On the other hand it had by far the largest Jewish population in the 19th and early 20th centuries. In Russia strong antisemitism always existed (based on official religion which was enforced by the state), and in the early years of the war many Jews living in the border areas were forcibly deported because of the alleged co-operation with the enemy.