About 15 North Korean pilots are believed to be involved in Syrian government attacks on Sunni insurgents, the London-based Syrian Observatory for Human Rights said Sunday.

They were seen in the cockpit of Syrian military helicopters during air strikes against rebel strongholds in Aleppo in northern Syria.

Al Durar, a website linked to the rebels, claimed that the Bashar al-Assad regime asked its ally North Korea for air force personnel as it struggles with defections among its own pilots.

Citing a source in Syria, SOHR reported in June this year that a dozen North Korean officers were spotted in the Syrian government's artillery unit.

