DHAKA - Bangladesh's central bank governor Atiur Rahman said on Tuesday he had resigned after $81 million was stolen from the bank's account at the New York Fed in one of the largest cyber heists in history.

Rahman told Reuters that Prime Minister Sheikh Hasina had accepted his resignation.

Unknown hackers breached the computer systems of Bangladesh Bank and transferred $81 million from its account at the Federal Reserve Bank of New York to casinos in the Philippines between Feb. 4 and Feb. 5.

Finance Minister Abul Maal Abdul Muhith earlier said the central bank did not inform him about the heist, and that he learned of it only a month later when news first appeared in the media.

"I am very much unhappy about the handling of the issue," he told reporters in his office in Dhaka.

The hackers breached Bangladesh Bank's systems last month and stole its credentials for payment transfers, two senior Bangladesh Bank officials said.

They then bombarded the Federal Reserve Bank of New York with nearly three dozen requests to move money from the Bangladesh bank's account there to entities in the Philippines and Sri Lanka, the officials said.

Four requests to transfer a total of about $81 million to the Philippines went through, but a fifth, for $20 million, to a Sri Lankan non-profit organisation got held up because the hackers misspelled the name of the NGO.

The full name of the non-profit could not be learned. But one of the officials said the hackers misspelled "foundation" in the NGO's name as "fandation", prompting a routing bank, Deutsche Bank, to seek clarification from the Bangladesh central bank, which stopped the transaction.

Deutsche Bank declined to comment.

At the same time, the unusually high number of payment instructions and the transfer requests to private entities - as opposed to other banks - made the Fed suspicious, which also alerted the Bangladeshis, the officials said.

The details of how the hacking came to light and was stopped before it did more damage have not been previously reported.

Bangladesh Bank has billions of dollars in a current account with the Fed, which it uses for international settlements.

The transactions that got stopped totalled between $850 million and $870 million, one of the officials said.

READ: How a hacker's typo helped stop a billion dollar bank heist