Alarming new reports indicate the Islamic State may still have a significant militant presence in Iraq and Syria despite the collapse of the caliphate.

The latest estimates suggest that the extremist organization may have anywhere between 20,000 and 30,000 troops in the two war-torn countries.

Although the group has suffered significant losses in recent years, the most recent reports suggest that ISIS has replenished its force, potentially to numbers as high as those at the peak of the group's power.

Tens of thousands of Islamic State jihadists are still waging war in Iraq and Syria, new reports reveal, suggesting that the global terrorist group may be far from defeated despite its battlefield losses.

There are still 28,600 to 31,600 ISIS fighters in Iraq and Syria, Voice of America reported Monday, citing Defense Department data. A United Nations panel of experts report concluded the same, revealing that ISIS may have anywhere between 20,000 and 30,000 troops in these countries despite the fall of the caliphate, the Associated Press reported Monday.

At the height of its power in 2015, ISIS controlled large swaths of territory stretching from Aleppo to Baghdad and had around 33,000 fighters in its ranks in Iraq and Syria, according to US military and intelligence officials. The US military claimed last summer to have killed 60,000 to 70,000 ISIS militants since US-led strikes began four years ago. The accuracy of these figures have at times been called into question.

The latest reports suggest that while ISIS has suffered significant losses in recent years, it has managed to maintain its strength, at least in terms of total troop numbers.

"Taken at face value, the US government is saying ISIS has the same number of fighters in Iraq and Syria today as when the [coalition] bombing campaign began," Thomas Joscelyn, a senior fellow at the Foundation for Defense of Democracies, explained to VOA, arguing that ISIS appears to have successfully replaced its entire force structure.

The tens of thousands of ISIS jihadists operating in Iraq and Syria include "a significant component of the many thousands of active foreign terrorist fighters," the UN report revealed. With many commanders killed and the terror group's once sprawling caliphate in shambles, ISIS is transitioning from a "proto-state" organization to a "reduced, covert version" of what it once was. This change is most evident in Iraq, where ISIS is suspected to have as many as 17,000 fighters under its command.

A wave of kidnappings, assassinations and bombings attributed to or claimed by the Islamic State in Iraq have stoked fears that the organization, believed to have been largely wiped out over the past year, is making a comeback, The Washington Post noted in mid-July.

Measuring troop numbers for ISIS in Iraq and Syria is difficult considering that there are no official records. In January, there were estimates suggesting that ISIS had as few as three thousand fighters in the two war-torn countries, while some observers argued that there were still as many as 10,000 loyalists in Iraq and Syria. While ISIS has taken a beating in Iraq and Syria, it still maintains a rather substantial presence in other countries and regions like Afghanistan, Libya, Southeast Asia and West Africa.

"There is hard fighting ahead. That's all there is to it," Secretary of Defense Jim Mattis said recently.