Iranian hackers have reportedly intensified their campaign against American firms, hacking into computer networks of several US energy companies, according to US officials.
A USA official was cited by the Wall Street Journal as saying that this is representative of stepped-up cyberactivity by the Iranian regime.
"The more they do this, the more our concerns grow," the official said.
"What they have done so far has certainly been noticed, and they should be cautious."
The latest attack was targeted at accessing control-system software that could authorise them to damage or destroy oil and gas pipelines in the future.
However, Iranian officials reject any involvement in hacking.
Iran spokesman at the United Nations, Alireza Miryousefi, said although Iran has been repeatedly the target of state-sponsored cyberattacks, attempting to target Iran’s civilian nuclear facilities, power grids, oil terminals and other industrial sectors, Iran has not ever retaliated against those illegal cyberattacks.
"In the lack of international legal instruments to address cyberwarfare, Iran has been at the forefront of calling for creating such instruments," Miryousefi said.
"We categorically reject these baseless allegations used only to divert attentions."
Earlier, Iran accused the USA of carrying out its own cyberattacks against the Islamic Republic.
Iran was alleged of involvement in hacking into several American banks, such as Bank of America, JPMorgan Chase & Co and Citigroup, as part of their broad cyber operation, while it rejected claims.
