The bank was also being probed by Sri Lanka's securities watchdog.
Update II Saliya Rajakaruna, retiring chief financial officer of Bank of Ceylon has been appointed chief executive.
From Thursday Zulfiqar Zavahir has retired from the post of chief executive. Deputy chief executive Iftikar Ahamed has resigned.
The bank's chief treasury manager also ceases to function, an official said.
Sarath Piyaratne, executive director will be chief executive until the new chief executive takes over.
Rajakaruna is a 30-year veteran with Citibank London. Rajakaruna joined Bank of Ceylon initially as its chief financial officer and later also functioned as its chief risk officer, NTB said in a stock exchange filing.
He is also credited with shooting down an oil derivative deal for Ceylon Petroleum Corporation and protecting the Bank of Ceylon from losses.
The changes came after NTB reported an 800 million rupee forex loss, which it said was in breach of operating procedures.