(Reuters) - The Institute of International Finance warned on Friday that further sanctions on Russia would have a "broader chilling effect on Russia" and its companies who are already largely excluded from raising foreign capital.

Of the four companies sanctioned by the United States on Wednesday, oil company Rosneft was most vulnerable due to its hefty financing requirements for the remainder of this year.

The IIF, a lobby group which represents 500 financial institutions including the world's major banks, said it expected further sanctions if an investigation established Russian links to the downing of a Malaysian airliner on Thursday.

(Reporting by David Chance Editing by W Simon)