Some were linked to last month’s attacks in Paris and planning further attacks on the West, US Army Colonel Steve Warren added.
He named one as Charaffe al-Mouadan, who he said had a direct link to Paris attack cell leader Abdelhamid Abaaoud.
Another was a UK-educated Bangladeshi computer systems engineer, he said.
The US-led coalition has been targeting IS in Iraq and Syria for over a year. Russia recently began its own air attacks against armed opponents of the Syrian government, including IS.
Syria-based Mouadan was killed in an air strike on 24 December, said Col Warren.
Another man with connections to the Paris attackers, Abdul Qader Hakim, died two days later in the northern Iraqi city of Mosul, he added.
- 27 years old, also known as Souleymane
- Grew up in Drancy, a poor north-eastern suburb of Paris
- Travelled to Syria in mid-2013
- Had a “direct link” to Abdelhamid Abaaoud and was “actively planning” more attacks, US says
- Childhood friend of Samy Amimour, one three jihadists who killed dozens at the Bataclan concert venue, in the deadliest attack on 13 November
- French media say investigators focused of Mouadan after interviewing a Bataclan survivor, who overheard one of the militants ask another if he was “planning to call Souleymane” – the reply was: “No, we’ll do it our way.”
Col Warren added that an earlier air strike, on 10 December, killed the UK-educated Bangladeshi computer engineer – who, he said, had supported IS hacking activities, anti-surveillance technology and weapons development.
“Over the past month we’ve killed 10 Isil [IS] leadership figures with targeted air strikes, including several external attack planners, some of whom are linked to the Paris attacks,” he said.
“Others had designs on further attacking the West.
“As long as Isil external attack planners are operating, the US military will hunt them and kill them.”
Abdelhamid Abaaoud, a Belgian national, was killed in a police raid in a Paris suburb just days after the 13 November attacks in the French capital which killed 130 people at multiple venues in the city. Most of the attackers also died.