Iran says a suspected cyberattack on its state-run oil industry had little impact on operations thanks to rapid measures taken by experts to limit the spread of the virus.

Iranian state news agency IRNA quotes an Oil Ministry official as saying there was “no damage” to the ministry's computer data from the virus, which authorities first detected on Sunday. Deputy Minister for Oil and Civil Defense Hamdollah Mohammadnejad also said Iranian oil production facilities have continued to operate without interruption. But he said it will take several days to investigate and resolve the issue.

Iranian authorities say they responded to the cyberattack by switching off Internet access at Oil Ministry offices and facilities, including the country's main terminal on Kharg Island, which handles three-quarters of Iranian oil exports.

Iran has periodically reported cyberattacks on its nuclear and industrial sectors.

The head of a U.S.-based energy research company told VOA that the latest digital assault on the Iranian oil sector is likely to have only a minimal impact on the country's oil production. International Petroleum Enterprises president Hossein Ebneyousef says Iranian oil terminals are “very low-tech” and have operated for decades without the Internet, using gravity rather than pumps to transfer crude from storage tanks to ships.

Ebneyousef says Iranian oil terminal workers also have other means to communicate when email systems are down, including telephones.

He says Iran has improved its response to cyberattacks since 2010, when its nuclear facilities were affected by the Stuxnet computer worm. Iranian authorities have accused the United States and Israel of trying to sabotage Iran's nuclear program through methods such as cyberattacks. Both nations accuse Iran of secretly trying to develop nuclear weapons and refuse to rule out any options for preventing such an outcome.

Iran says its nuclear program is peaceful.