CAIRO (Reuters) - Egypt's largest listed bank, Commercial International Bank, has tightened limits on pound-linked debit cards used overseas for the third time in six weeks as the country grapples with a shortage of dollars.

Egypt's ability to import has been hampered since a 2011 uprising drove away tourists and foreign investors, both crucial sources of hard currency.

The country's foreign reserves fell to $16.564 billion in August from around $36 billion before the revolution.

The central bank has been rationing dollars through weekly sales, keeping the Egyptian pound artificially strong at 8.78 per dollar.

CIB is planning, as of Sept. 9 to halt cash withdrawals in foreign currency from its local debit cards used abroad. It has also reduced by 70 percent the amount that customers can charge purchasing goods abroad using debit cards but it did not change its limits on credit cards.

The details were set out in a document to clients seen by Reuters.

CIB cut Classic Card holders' maximum purchase limits outside of Egypt to $50, to $150 per month for Titanium cardholders and to $300 a month for Platinum cardholders.

In early August the bank reduced its withdrawal and purchasing limits using foreign currency from local debit cards and credit cards by around 50 percent and then by around 60 percent in mid-August.

(Reporting by Ehab Farouk; writing by Asma Alsharif)