The US has carried out a secret cyber operation against Iran, targeting its ability to disseminate propaganda in the wake of last month’s attacks on two Saudi oil facilities — which Washington blames on Tehran, according to a report.

Two US officials told Reuters on condition of anonymity that the operation took place in late September. One of them said the strike targeted hardware, but did not provide additional information.

Mohammad Javad Azari-Jahromi, Iran’s minister of communications and information technology, responded to the report by telling the Fars news agency: “They must have dreamt it.”

The Pentagon declined to comment about the operation.

“As a matter of policy and for operational security, we do not discuss cyberspace operations, intelligence or planning,” Pentagon spokeswoman Elissa Smith told Reuters.

The strike appears to have been more limited than other such operations against Iran after the downing of a US drone in June and an alleged attack by Iran’s Revolutionary Guard on oil tankers in the Gulf a month earlier, according to the news outlet.

The US, Saudi Arabia, Britain, France and Germany have publicly blamed the Sept. 14 attack against the oil facilities on Tehran, which denied any involvement.

The Iran-aligned Houthi militant group in Yemen claimed responsibility.

The Pentagon has responded to the strikes by dispatching thousands of additional troops and equipment to bolster Saudi defenses.

It could take months to determine the impact of any cyber strikes, which are seen as a less provocative option than a conventional military assault.

“You can do damage without killing people or blowing things up; it adds an option to the toolkit that we didn’t have before and our willingness to use it is important,” James Lewis, a cyber expert with the Washington-based Center for Strategic and International Studies, told Reuters.