Egypt's central bank placed a time limit on the tenures of CEOs of commercial lenders on Thursday, setting in motion a purge of several top executives that puts it on a likely collision course with the country's banking sector.

To help modernise the sector and "inject new blood", chief executives of public and private banks as well as the heads of foreign banks operating in Egypt would have to quit after nine years, the central bank said in a statement.

The decision will force eight top executives to resign their positions, a senior banking official told Reuters. They include Commercial International Bank's Hisham Ezz al-Arab and Arab African International Bank's Hassan Abdalla.

Shares in CIB were down 1.7 percent at 1126 GMT.

There was no immediate comments from the country's leading banks on the measure, which drew criticism from Hany Tawik, head of Egypt Private Equity Association, a group that represents business community interests.

"This is interference in an essential right of the general assembly to appoint someone that is best suited for them. It's my right as a shareholder to choose the head of the bank," he said.

The central bank has recently taken steps to alleviate a deepening foreign currency crisis: devaluing the Egyptian pound, lifting caps on foreign deposits and withdrawals, and injecting hundreds of millions of dollars to free up import activity.

Its foreign reserves have tumbled to $16.5 billion in February from around $36 billion before the 2011 uprising that ousted long-time leader Hosni Mubarak, driving away tourists and foreign investors that were key sources of foreign currency.

Around 40 public and private sector banks operate in Egypt.

Both consecutive and non-consecutive CEO terms will count towards the nine-year limit, the central bank said.