“We support the government of Iraq. We are very disturbed by the lack of security in Iraq, especially the daily killings of the Iraqi people,” Khamenei said in a sermon at Tehran University.

“American machine-guns are criminal, but those elements who plant bombs are also criminals,” he added.

US Defence Secretary Donald Rumsfeld said on Tuesday that US forces had found Iranian weapons inside Iraq on more than one occasion over the past couple of months, accusing Tehran of seeking to replicate its own Islamic regime in Iraq by backing insurgents.

But Khamenei said the US was behind the regular bombings, arguing that Washington needed a “pretext” to stay put in Iraq.

“For us, the prime suspect in these incidents is America, because terrorism in Iraq functions under the eyes of the US. Thousands of American forces are spread across Iraq and if they wanted to eradicate insecurity they could have,” he said. “There are some signs which point to the spy services of the US and Zionist regime,” he said.