Iraq's military says a drone attack on the residence of Prime Minister Mustafa al-Kadhimi was a carefully planned assault.
Kadhimi escaped unharmed when his home in the capital of Baghdad was attacked by explosive-carrying drones on Sunday. Several security guards were injured.
A government investigative team that includes bomb experts on Monday found that three drones were involved in the attack, two of which were shot down.
A spokesperson for the Iraqi military told a state-run broadcaster and others that the drones took off from a location about 12 kilometers northeast of the prime minister's residence, and flew at a low altitude to avoid detection by radar.
Reuters news agency quoted a security official as saying the drones were made in Iran and of the same type as those used in attacks on US forces stationed in Iraq.
The official suggested an Iran-backed militia group was responsible for Sunday's assassination attempt.
Militia groups have denied involvement, but a coalition of militia-backed parties lost a significant number of seats in last month's parliamentary election.
Iraq's security forces have been involved in clashes with demonstrators who claim the election was rigged.