Two pilots working for Turkish Airlines have been abducted at gunpoint in Lebanon, near Beirut's international airport.
The men were snatched from a bus carrying several other crew members and passengers between a hotel and the airport terminal. The kidnapping occurred just a few metres away from an army checkpoint.
A group called Zuwwar al-Imam Rida has said it seized the men, saying it was in retaliation for the seizure of nine Lebanese Shia pilgrims in Syria in May last year.
Zuwwar al-Imam Rida said the pilots would be freed in exchange for nine Lebanese hostages in Syria.
The Turkish foreign ministry issued a statement on Friday urging its citizens to avoid non-essential travel to Lebanon. It advised those already there to leave or to take measures to ensure their personal safety.
Turkey backs Syria's Sunni rebels, and is seen to have influence over them, while much of Lebanon's Shia community supports President Bashar al-Assad, the BBC reports.
The nine Lebanese Shia pilgrims went missing in Aleppo province in northern Syria in May 2012 as they returned from a pilgrimage in Iran.
The Northern Storm brigade, a Syrian opposition group operating near the Turkish border, said it had carried out that abduction.