WASHINGTON — A senior US military official for the first time says the US-led coalition has killed 50,000 Islamic State militants in the last two years in Iraq and Syria.

The official said it was a conservative estimate, but it's a bit more than what others have stated before.

CIA: ISIS has 20,000 to 31,500 fighters, The Hills, Sep 11 2014

The CIA estimates the Islamic State in Iraq and Syria (ISIS) is made up of anywhere between 20,000-31,500 fighters, according to reports Thursday night.

The agency previously put the number at 10,000 but revised it upward after stronger recruitment since June, according to CIA spokesman Ryan Trapani, who was quoted in The Associated Press.

While ISIS forces come to existence seemingly out of nowhere only to get killed by the U.S. military, civilians in east-Aleppo vanish into the nowhere whenever the Syrian government forces take new areas.

UN diplomat offers to personally escort 900 al-Qaeda fighters out of Aleppo in hope of ending bombing, Telegraph, Oct 6 2016

Speaking in Geneva [UN envoy Staffan de Mistura] said that around 900 members of al-Nusra were still in Aleppo and he asked the jihadists to "look at my eyes" and decide if they were prepared to stay in the city even if it meant more casualties among the 275,000 civilians in the area.

"A thousand of you are deciding on the destiny of 275,000 civilians," he said. "If you did decide to leave [Aleppo] with dignity and with your weapons, to Idlib or anywhere you wanted to go, I personally am ready physically to accompany you."

Rebels defiant as Syrian army nears Aleppo's Old City, Reuters, Dec 4 2016

The U.N. estimates that close to 30,000 people have been displaced by the latest fighting, 18,000 to government-held areas, a further 8,500 to the Kurdish-controlled neighborhood of Sheikh Maqsoud and the rest within rebel-held areas.

U.N. envoy Staffan de Mistura has said more than 100,000 people may still be in the rebel-held area.