US forces shot down an Iranian drone aircraft that ventured inside Iraq several weeks ago, a senior Iraqi military official said on Monday.

"An unmanned Iranian plane crossed the border and it was discovered by multi-national forces' radar. They intercepted it and brought it down ... an American plane brought it down," Major-General Abdul Aziz Mohammed Jassim, head of military operations at the Iraqi Defence Ministry, told Reuters.

The US military in Iraq has declined comment. It has accused Iran of arming militants and meddling in neighbouring Iraq, where tens of thousands have died in sectarian violence since the US-led invasion to oust Saddam Hussein in 2003.

"According to the report received by multinational forces, this drone entered Iraq mistakenly at a point 100 km (60 miles) from Baghdad. It crossed 10 km (6 miles) into Iraq. It's most likely that its entrance (into Iraq) was a mistake," Jassim said.

Jassim said he could not recall the precise date of the incident, but said it likely took place in late February. - Reuters