Qatar National Bank (QNB) has launched an investigation into an alleged security breach, which led to 1.4GB of customer database being leaked online.

Leaked documents include the bank details, telephone numbers and dates of birth of several journalists for Doha-based state-funded broadcaster Al-Jazeera, supposed members of the ruling Al-Thani family, and government and defence officials, a local news website reported on 27 April.

Hacking news portal Hackread, however, reported the incident a day earlier, citing that a group of unknown hackers claimed to have hacked into QNB’s database.

”The massive data dump appears to contain hundreds of thousands of financial records including credit card numbers and their personal identification number (PIN) codes, as well as customer transaction logs,” the portal said. “Moreover, the hackers also claimed to have leaked banking details of the Al-Thani royal family and Al-Jazeera journalists.”

It added that a folder among the leaked data is labelled as “spy”, which would catch the attention of anyone who has the access to the leaked data. The folder was found to have the financial details of what appears to be UK intelligence service MI6, the Qatari Defence Ministry and Qatar State Security Bureau (Mukhabara).

QNB is the largest lender in the Middle East and Africa by assets. It reported a 7 per cent increase in profits to almost $800m in the first quarter of 2016.

The bank said it was investigating “social media speculation in regard to an alleged data breach” and would not comment on reports circulated via social media. It also said the alleged hack had no financial impact on its clients or on the bank itself.

Middle Eastern lenders are attractive targets for cyber criminals because of the high levels of wealth fuelled by hydrocarbons exports. Qatar in particular has the highest GDP per capita in the world.

The last major reported cyber-attack in the Gulf region was in 2013, when hackers were alleged to have stolen $45m from Oman’s Bank Muscat and National Bank of Ras al-Khaimah in the UAE, according to a report by UK news agency Reuters.

A survey conducted earlier this year among 700 professionals in the GCC found that roughly half of the businesses in the region are vulnerable to cyber attacks.