A high-ranking military source told AFP that the plane crashed during a reconnaissance flight near Kirkuk and that its three crew were considered missing.
The military source said authorities had launched a search for the crew after the Cessna 208 Caravan went down near Kirkuk, around 220 kilometres north of Baghdad.
In its combat version, the aircraft can be used to launch laser-guided Hellfire missiles.
The Islamic State jihadist group claimed in a statement posted on Twitter and a video released moments later that its fighters had shot the plane down, killing five crew members.
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A video -- which claims to show the moment the aircraft was shot down -- released by the jihadist organisation shows the wreckage of a plane that could be a Cessna Caravan.
The footage also shows IS fighters celebrating around body parts, some of which are floating in a small canal.
Iraqi forces have been making gains against the jihadists in recent months as they seek to reclaim territory seized by IS during a major offensive in 2014.
The pressure has mounted on anti-IS forces to flush the jihadists out of the Hawijah area after a chemical attack was launched from the nearby village of Bashir last week.
The suspected mustard agent attack on the Kurdish-controlled town of Taza killed a three-year-old girl and left hundreds of people complaining of burns and respiratory problems.
The town's residents have demanded government action to retake Bashir, which is visible from the main road between Baghdad and Kirkuk, but has remained in IS hands since 2014.
Prime Minister Haider al-Abadi has responded by promising that an operation against Bashir would get under way soon.
A senior military official in Kirkuk said that such an operation would further increase the pressure on Hawijah, which is IS's main remaining hub east of the Tigris.