Al-Qaida is trying to regain its primacy over international militancy as Islamic State loses ground, a senior NATO official said on Tuesday, seeing a potentially increased risk to the West from the groups' rivalry.

But Arndt von Loringhoven, the alliance's assistant secretary-general for intelligence and security, said Islamic State retained some personnel strength despite its combat losses, including fresh recruits among women and children.

"ISIS-Daesh weakening has provided al-Qaida with an opportunity to attempt to regain its former status," Von Loringhoven told a security conference hosted by Israel's IDC Herzliya college, using a term for Islamic State.