Cyber-attacks on Iran have forced the country to beef up its defences, with the result that the country's cyberwar capabilities have become far more complex, a US general has said.

General William Shelton, who heads up the US cyber ops, told reporters during a briefing that Iran had responded to repeated computer virus attacks by rapidly improving its cyber-capabilities, the BBC, Reuters and others reported.

Shelton also warned that the country's new proficiencies wouldn't just be used to defend itself.

"They are going to be a force to be reckoned with," he said, "with the potential capabilities that they will develop over the years and the potential threat that will represent to the United States."

Iran's main uranium enrichment site in Natanz was attacked in 2010 by the Stuxnet virus, widely thought to have been the work of the Obama administration. Since then its corporations have been hit by numerous viruses, including a return of Stuxnet at the end of last year.

Some in the US, in turn, have blamed Iran for a series of cyber attacks on banking websites last September, including those of JP Morgan Chase, Bank of America and Wells Fargo, but the country has denied responsibility.

“Iran respects international law and refrains from targeting other nations’ economic or financial institutions,” the country's state-run Press TV news channel reported its officials as telling the UN. ®