About $19.5 million was taken when the bank was updating a computer system in the East African country, meaning ATM and online transactions were not reflected in affected accounts for five hours overnight March 15-16, according to the Commercial Bank of Ethiopia (CBE).

"The bank warns that it will take legal action against those who do not return the money within this period," CBE said in a statement Wednesday, extending the deadline to return the money from March 23 to March 30.

"We will publish your names and photos in various mass media and declare that you are suspected of committing illegal money transfers."

People rushed to ATMs and multiplied transfers after the glitch was widely shared online, especially in student groups, according to local media.

Some reports put the bank losses as high as 100 million dollars.

More than nine thousand customers "voluntarily" returned money before the first ultimatum, with 5,166 named customers left to pay, the state-owned bank added.

About 80 percent of the money initially withdrawn or transferred has been repaid, the CBE said on Tuesday.

Founded in 1963, the bank boasts 40 million customers and over 1940 branches in Africa's second most populous country of 120 million people.