Iraq's foreign minister said Wednesday that foreign assistance in the fight against the Islamic State jihadist group should respect the country's sovereignty.

He hailed the role played by Iran, which Kurdish officials said has been actively taking part in the fighting and still maintains a force on Iraqi territory.

"We cannot accept that Iraq is becoming a land of conflict but we have to solve this problem in a way that preserves Iraqi sovereignty," Ibrahim al-Jaafari told a news conference.

When asked about a comment in which the commander of Iran's ground forces last week vowed to protect his own border "deep into Iraqi territory" if necessary, Jaafari said Iranian support was welcome.

"Iran has provided assistance to Iraq, as have some other countries. This is not a secret and we have to thank them for it," he said.

Iran has been a close ally of Iraq's Shiite-dominated government, and Jaafari spent a whole decade in exile there when Baghdad was under Saddam Hussein's rule.

Critics have questioned the legal basis and motives for Iran's participation in the government's military efforts against the jihadists, who have conquered swathes of Iraq since June.

Iranian troops have been posted on the Iraqi side of the border in the south of Kurdistan while Tehran is also reported to play a key role in training and running some of Iraq's Shiite militias.

Kurdish officials said there were about 100 Iranian troops posted in the Khanaqin area, some 150 kilometres (95 miles) northeast of Baghdad.

- Mortar experts -

"The centre of Khanaqin is only five kilometres away from Iran, it's as if it was in Iran," said General Jaafar Sheikh Mustafa, the Kurdistan Democratic Party's local leader.

"There are oil wells there that are very important and Iran has to defend itself, that's why they have sent a military unit, the Sabai Pasdaran Khorasan," he told AFP.

"In the Khanaqin region, the Sabai Pasdaran Khorasan, the Iraqi forces and the peshmerga fought together in the battle for Jalawla," he said.

Jalawla, which has been one of the main flashpoints in Iraq since the Islamic State group launched a devastating offensive in Iraq four months ago, lies just 30 kilometres from the border.

Mustafa said 600 Iranian troops moved across the border in June and July.

"There are only 100 of them left to keep an eye on the situation, most of them mortar specialists," the general said.

The Patriotic Union of Kurdistan, the other historical party in the autonomous region, has had close ties with Iran over the years.

Iran "plays a very important role in the Middle East, especially in Iraq. If Iran is active in the Iraqi conflict, it will be easier to solve," Kurdish peshmerga forces spokesman Halgord Hekmat said.

"The Iranians were in Amerli," he said of a Turkmen Shiite town that the jihadists besieged for more than two months.

A joint push also involving the peshmerga, federal forces and Shiite militias broke the siege in late August, one of the biggest victories for Baghdad since the June debacle.

Hekmat said Iranian forces had also been deployed in Makhmur, about 60 kilometres southeast of Arbil, "to provide assistance, just in case".