** Shares in Portugal Telecom fall 5.6 pct after Brazil's Oi slides on exit of chief executive Zeinal Bava.
** Traders cite growing uncertainty for the outlook as Bava's departure may hasten sale of PT assets in Portugal.
** Bava said on Tuesday he would resign as chief executive of Oi, potentially paving the way for a sale of the company's Portuguese assets.
** Bava joined Oi in June 2013 with the goal of pushing through a merger with Portugal Telecom. That deal came under pressure after a holding company of Portugal's Espirito Santo banking family defaulted on nearly 900 million euros it owed to Portugal Telecom, forcing a revamp of the merger deal.
** Bava resigned after reports that billionaire Patrick Drahi's telecoms firm Altice SA was in talks to buy Oi's Portuguese assets, which became part of Oi after the merger.
** "At this stage, there are more doubts than certainty," said Albino Oliveira, analyst at brokerage Fincor. "The market is reflecting the uncertainty about what will happen next."
** Stock down 51.4 pct YTD.
Reporting By Daniel Alvarenga, writing by Axel Bugge