But Iraqi General Qais al-Mohamadawi, part of the anti-jihadist coalition, stressed that IS -- now based in remote desert and mountain hideouts -- has "lost its ability to attract new recruits".

The United Nations estimated in a report published last month that IS still has "5,000 to 7,000 members and supporters" across Iraq and neighbouring Syria, "roughly half of whom are fighters".

The IS extremists in 2014 launched their self-proclaimed "caliphate" across swathes of both countries in a campaign marked by its brutality including mass killings, torture, rape and slavery.

US-backed counter-offensives ended their territorial hold in Iraq in 2017 and in Syria in 2019, but IS cells continue to target security forces and civilians in both countries.

With thousands of suspected IS fighters and relatives now held in vast detention camps, US General Michael Kurilla, head of Central Command, warned Saturday of the persistent threat of an "ISIS army in detention", using an alternative acronym for IS.

General Mohamadawi, deputy commander of the Iraqi operations unit working with the international anti-jihadist coalition, said Sunday that hundreds of IS fighters remain active in Iraq.

"According to information from intelligence agencies, the total number of IS members does not exceed 400 to 500 fighters, in three or four provinces," he told a press conference.

The group has "lost its ability to attract new recruits," he added, also pointing to a February 26 military operation that had killed 22 IS members and destroyed a "training camp" in Al-Anbar province.

The UN report last month said IS had been much depleted by "sustained counter-terrorism operations" in both countries.

It said the group still operates cells of around 15 to 30 individuals across Syria and continues "guerrilla warfare tactics" against government forces, other fighters and civilians.

In Iraq, IS cells operate in rural mountain areas, "leveraging the porous Iraqi-Syrian border and retaining manoeuvrability to evade attacks" while trying to "rebuild and recover", the UN report said.

The report estimated IS's "dwindling cash reserves" at $25 million to $50 million and said it had started investing in hotels and real estate to launder money and engaging in cattle rustling to raise funds.