At least 13 Tanker Pacific ships, owned by the Israeli Ofer Brothers Group, have docked in Iran over the past decade, according to information released by Equasis, a major shipping information database.

On Tuesday the U.S. State Department shocked the Israeli business community with its announcement that the Ofer Brothers shipping company had violated economic sanctions against Iran. At the heart of the matter was an oil tanker named Raffles Park, which had been owned by the Ofer Brothers Group and eventually found its way into the hands of the Iranian national shipping company - the Islamic Republic of Iran Shipping Lines.

The ships docked in the Iranian port city Bandar Abbas and Kharg Island. Bandar Abbas is a city located on Iran's southern coast. Kharg Island is used as a port for exporting oil from Iran.

Iran, who refuses to recognize Israel's right to exist as a Jewish state, has denied all ties to the Ofer family. "Any commercial connection to the Zionist regime and the companies that operate within it are against the law," an Iranian official said.

The Ofer Brothers Group denies the allegations against them.

A state department spokesman, Mark Toner, replied to the Ofers' claims at a press conference on Wednesday.

"We did considerable due diligence in checking out these claims. And what we found is that Ofer Holdings Group is the parent of a company called Tanker Pacific, and that's the company that actually sold this tanker to the Iranians," Toner said.

Toner said Tanker Pacific and its subsidiary had "failed to do proper due diligence and to prevent this transaction. So they're responsible - I guess my point is that they'd be responsible for the conduct of their subsidiary."

The alleged business with Iran was done by the Singapore-based Tanker Pacific, one of the world's largest shipping companies and an Ofer Brothers subsidiary. It operates a fleet of 45 huge tankers that transport crude oil worldwide, with branches in India, Britain and China.