The Islamic State (ISIS) appears to be both losing and winning in its campaign of terror in the Middle East and elsewhere.

A senior U.S. military official has revealed that at least 50,000 ISIS militants have been killed since 2014 when the U.S.-led coalition started fighting the Islamist extremist group in Iraq and Syria. The unnamed official even underscored that that figure was just a "conservative estimate," the BBC reported.

"I am not into morbid counts but that kind of volume matters, that kind of impact on the enemy," the official said on Thursday, adding that the ISIS fatalities resulted mostly from the use of the coalition's air power.

In August, Lt. Gen. Sean MacFarland was quoted by the Associated Press as saying that about 45,000 ISIS combatants had already been killed by coalition forces.

Before these disclosures, the U.S. had often been reluctant to provide figures on enemy casualties, the BBC noted.

The figures mentioned, however, do not seem to tally with the statement issued in February by White House Press Secretary Josh Earnest who said that ISIS had about 25,000 fighters operating in Syria and Iraq, citing a U.S. intelligence estimate.

But the latest reported death toll for ISIS is already double that number.

The BBC noted though that the U.S. has repeatedly warned that ISIS can replace its fighters rapidly, which could explain the disparity in the figures of ISIS fatalities and the estimated number of its fighters.

Aside from the reported loss of a large number of fighters, the ISIS has also lost some of the territories it captured in Syria and Iraq as its forces continue to get pounded by U.S., British, Russian, Turkish, Iraqi, Syrian and Kurdish forces, the BBC said.

ISIS is keeping its grip though on Mosul in Iraq, Raqqa in Syria and the Sunni Arab tribal heartland of the Euphrates river valley, which stretches from eastern Syria to western Iraq.

But even as ISIS continues to suffer battlefield defeats in the Middle East, NBC News has reported that the terrorist organisation has extended its reach to more countries in Asia and Africa—from 13 countries in 2015 to 18 this year.

In fact, in 2014, ISIS was only operating in seven nations based from U.S. State Department documents, NBC said.

"The current briefing map shows 18 countries where ISIS is fully operational. The map also displays a new category — 'aspiring branches' — and lists six countries where they're taking root: Egypt, Indonesia, Mali, the Philippines, Somalia and Bangladesh," the news agency stated based from an exclusive classified map it obtained showing the global expansion of the terror group.