For the second time in the space of five months, a hacker group is claiming it has knocked out communications on a swathe of the Iranian merchant fleet. 

The hacker group called Lab Dookhtegan, which translates as Sewn Lips, told London-based TV channel Iran International it had hacked into the systems of the National Iranian Tanker Company (NITC) and the Islamic Republic of Iran Shipping Lines (IRISL), disrupting operations and communications from ship to shore on 39 tankers and 25 containerships.

The hackers said the breach was carried out by infiltrating Fanava Group, an Iranian IT and telecoms holding company that provides satellite communications, data storage, and payment systems.

In March this year, the same group claimed to have disrupted communications on a total of 116 vessels belonging to the same two state-owned Iranian shipping firms.