The US Treasury Department has extended weapons-related sanctions against Iran to 10 additional businesses and five individuals it said were affiliated with state-owned Bank Mellat and Islamic Republic of Iran Shipping Lines.

The Treasury Department previously blacklisted Bank Mellat and IRISL under sanctions targeting alleged supporters of what the US describes as Iran's nuclear weapons development program.

The latest actions prohibit US entities from any transactions with the designated firms and individuals, and seek to freeze assets they may have under US jurisdiction.

Similar moves in the past also have effectively cut off international financing to sanctioned entities.

The Treasury Department said the sanctions were extended to eight 'front company' subsidiaries of IRISL, all located in the Isle of Man, a self-governed British territory. Each is the registered owner of a vessel previously identified as having been owned by IRISL, the Treasury Department said.

The shipping firms use the names Ashtead, Byfleet, Cobham, Dorking, Effingham, Farnham, Gomshall and Horsham.

Also designated were Pearl Energy and its subsidiary, Switzerland-based Pearl Energy Services, which the Treasury said were formed by a subsidiary of Bank Mellat.

Pearl Energy provides economic research, while Pearl Energy Services' mission is to provide financing and expertise to entities seeking to enter Iran's petroleum sector.

Recent United Nations sanctions against Iran severely restrict the ability of foreign firms to participate in the Iranian energy sector. – Reuters