Gunmen kidnapped two Turkish Airlines pilots early Friday on a road leading out of Beirut airport, in an apparent bid to secure the release of Lebanese pilgrims held in Syria.
Turkey condemned the pre-dawn abduction and urged its citizens to leave Lebanon as the operation raised new fears that Lebanon is being dragged further into the Syrian conflict.
Lebanon Interior Minister Marwan Charbel said the pilots were forced off a bus taking them and other crew to a hotel in the city.
"A kidnapping operation took place at 3:00 am targeting a bus carrying several members of a Turkish Airlines crew going from the airport to the hotel," Charbel told AFP.
"Gunmen kidnapped two passengers from the bus, the pilot and co-pilot."
Lebanese sources said four gunmen ambushed the bus, taking only the pilots and leaving seven crew who were flown home later on Friday.
The kidnapping took place just outside the airport perimeter in an area abutting neighbourhoods dominated by the Shiite groups Hezbollah and Amal.
A previously unknown group calling itself Zuwwar Imam Ali al-Rida claimed responsibility for the abduction, saying it was carried out to secure the release of nine Lebanese kidnapped in Syria last year.
"We announce that captain Murat Akpinar and his co-pilot Murat Agca are our guests until the release of our brothers who were kidnapped in Aazaz (Syria)," said the group in a statement.
They also said Turkey would be held "directly responsible for the freedom" of the Lebanese.
Turkish foreign ministry spokesman Levent Gumurukcu said his country has no link to the disappearance of the Lebanese pilgrims in Syria.
"We have seen claims of responsibility... The Lebanese authorities are checking that," Gumurukcu told AFP.
Asked about a link with the missing Lebanese, he said: "If this is the case, it is definitely very wrong: we have nothing to do with that and out of humanitarian concern, Turkey has already been doing all it can" to obtain their release.
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The pilgrims disappeared in Syria's northern Aleppo province in May 2012 after touring Iranian holy sites, including the shrine of revered Shiite religious figure Imam Ali al-Rida.
As Lebanon launched an investigation, relatives of the Lebanese pilgrims welcomed the abduction of Turkish nationals but stressed they were not involved.
"We condemn kidnappings in principle, but in this particular case, we support it and we congratulate those who carried it out," Hayat Aawali, the wife of one of the nine men, told Lebanon's Al-Jadeed television.
"We thank them for what they have done; we couldn't have done it ourselves."
Relatives of the kidnapped Lebanese have staged protests outside the offices of Turkish Airlines in Beirut over the past year, to press Ankara to help release the men.
Turkey is a strong backer of rebels fighting to topple Syrian President Bashar al-Assad, including the mainstream Free Syrian Army which has denied any involvement in the disappearance of the Lebanese pilgrims.
Turkish Foreign Minister Ahmed Davutoglu telephoned Lebanese parliament speaker Nabih Berri -- head of the Shiite Amal movement -- and Prime Minister Najib Mikati over the incident.
Mikati said he "condemned this act and I told him that we are doing everything in our power to identify the kidnappers and to free" the pilots.
Nevertheless Turkey urged its citizens to leave Lebanon and warned others against travelling to the Mediterranean country.
"Given the current situation it is vital that our citizens avoid all travel to Lebanon," the foreign ministry said.
"We suggest that citizens who are still in Lebanon return to Turkey if they can, or if they have to remain, to take all measures to ensure their personal safety and be vigilant."
A Lebanese government source said the abduction came after those holding the pilgrims failed to uphold a deal to free them in return for the release by the Syrian government of 134 women prisoners.
The Syrian conflict, now in its third year, has raised sectarian tensions in Lebanon and contributed to an economic crisis in the country which is hosting more than 600,000 Syrian refugees.