In the first week of July, the Bangladesh Bank and Islami Bank Bangladesh completed a US dollar-taka trade, a typical mutual currency deal, which was supposed to replenish the central bank's dwindling forex reserves and provide the cash-strapped Shariah-based lender with some liquidity support.

The central bank was supposed to receive $550 million in exchange for providing Tk 6,490 crore to Islami Bank.

It sounds like a win-win deal. However, central bank documents show that only $100 million was actually deposited into the central bank's account.

The remaining $450 million was not provided to the BB until August 11, well after the political changeover had led to major shake-ups to both the central bank and the Shariah-based lender.

A senior central bank official alleged that former Governor Abdur Rouf Talukder and other high-ranking officials in the central bank's Forex Reserves and Treasury Department were complicit in "objectionable forex trading" to benefit Islami Bank Bangladesh.

They allege that the decision ultimately benefitted the controversial S Alam Group, the then majority stakeholder and apparent controller of Islami Bank.

Although new central bank Governor Ahsan H Mansur today termed the incident "unexpected" and said the dues have already been adjusted, economists called to identify and punish culprits.

On July 3 this year, during Abdur Rouf Talukder's tenure as governor of the central bank, the BB injected Tk 6,490 crore into the struggling Islami Bank in exchange for $550 million, according to central bank documents.

On paper, $550 million was added to the foreign exchange reserves, with the BB purchasing the forex at a rate of Tk 118 per dollar.

However, gross forex reserves stood at $25.92 billion at the end of July compared to $26.81 billion on June 30, as per central bank data.

On August 11, the central bank's Forex Reserves and Treasury Management Department took steps to adjust the remaining $450 million. It deducted Tk 5,310 crore, equivalent to $450 million, from Islami Bank's current account.

As a result, BB officials reported that Islami Bank's current account balance turned negative again.

Md Kabir Ahmed, executive director of the Forex Reserve and Treasury Management Department, told The Daily Star that those forex deals were conducted in line with instructions from former governor Talukder.

He added that the central bank had fined Islami Bank $3 million for non-payment of the dues.

The Daily Star tried multiple times to reach former BB governor Talukder for comment, but he was unavailable.

Md Mezbaul Haque, executive director and spokesperson of the Bangladesh Bank, could not be reached over the phone until this report was filed.

Similarly, Islami Bank managing director Mohammed Monirul Moula and board chairman Md Obayed Ullah Al Masud were also unavailable.

However, an official at the Public Relations Department of the Shariah-based bank said that the board chairman and managing director would speak to the media after a scheduled meeting with the central bank governor on Thursday.

Central bank Governor Ahsan H Mansur today told journalists that it was unexpected from the central bank.

He said the forex trading dues have already been adjusted.

However, Mustafa K Mujeri, a former chief economist of the Bangladesh Bank, believes the culprits should be identified and punished.

"We see many such irregularities in the past which are coming now out. Many such unethical benefits have been given to protect the interests of some individuals and institutions, which should be properly investigated," said Mustafa K Mujeri.

"Those who were involved in the irregularities should be punished without delay," said the economist.