Four suspected militants have been detained in Afghanistan after attempting to fly to Saudi Arabia.
Three were arrested at Kabul airport but one boarded a flight that had to be ordered to return to Kabul, an Afghan intelligence source told the BBC.
The arrests came after tip-offs from US intelligence agents, the source said.
One of the detainees is a suspected member of the Haqqani network, an insurgent group with links to al-Qaeda, Nato said.
He was wanted in connection with attacks against Afghan and international troops, Nato said.
The Afghan intelligence source told the BBC that a phone conversation intercepted by American agents had given the men away.
Security personnel and the airport then lost track of the men before three of them were arrested. One was able to board a plane bound for the Hajj pilgrimage in Saudi Arabia.
The pilot was warned that fighter jets would be deployed if he did not turn around, the Afghan source said.
The plane did eventually turn around, but the BBC understands it flew for at least an hour, almost as far as the border with Iran in western Afghanistan, before the alert was raised.
Once the plane landed in Kabul Afghan security forces then went on board to arrest the fourth man, who was unarmed.
All four were held for questioning.