Saudi Arabia, the United Arab Emirates (UAE), Qatar and Kuwait have urged their citizens to leave Lebanon amid signs that the conflict in Syria is spilling over into its western neighbor.
The four Arab states urged immediate action after a string of kidnappings of Sunni Muslims by a powerful Shia clan.
They were retaliating for the abduction of a clan member by rebels in Damascus.
Meanwhile, a summit of Islamic countries meeting in Mecca has suspended Syria’s membership.
The Organisation of Islamic Co-operation’s secretary-general, Ekmeleddin Ihsanoglu, said the body had no room for a regime that kills its own people.
Correspondents say the move further isolates President Bashar al-Assad after the Arab League suspended Syria last November.
Lebanese citizens were further caught up in the Syrian crisis on Wednesday when warplanes struck the town of Azaz north of Aleppo, reportedly killing 30 people.
Among those reported wounded in the attack close to Syria’s border with Turkey were seven Lebanese hostages held by the rebels since May. Four more hostages were said to be missing after the building they were in was hit.
After unconfirmed TV reports that the four had died, rioters were said to have burned tyres on the main road to Beirut airport and an Air France flight switched routes to Jordan “for security reasons”.
The al-Meqdad clan said it had abducted more than 20 people it claimed were connected to Syrian rebels. A video broadcast by a pro-Syrian TV channel showed what it said were two of the men, apparently including a Free Syrian Army captain.
Although most of the men abducted were Syrians, a Turkish businessman and a Saudi national were also reported to be among those seized.
Syrian rebels say the man they seized in Damascus was fighting for the Syrian government on behalf of Lebanon’s Shia Hezbollah movement.
A video of Hassan Salim al-Meqdad was released by his captors on Tuesday in which the captive, surrounded by three masked gunmen, says he was one of 1,500 Hezbollah fighters who arrived in Syria in early August. The statement was dismissed by his family – the al-Meqdad clan – as a lie.
The clan, who are thought to be heavily involved in smuggling, have been described as a family with a military wing.
Saudi Arabia, Qatar and Turkey are all Sunni Muslim countries that support the Syrian rebels fighting the government of Bashar al-Assad.
As the al-Meqdads threatened to carry out further abductions, the official Saudi news agency Spa quoted a foreign ministry official as saying Saudi citizens should avoid “travelling to Lebanon for their own safety”.
A UAE foreign ministry official said it issued its alert after the embassy “received information about UAE nationals being targeted and because of the difficult and sensitive circumstances in Lebanon”, state news agency Wam reported.
Lebanon is a popular tourist destination for Saudis and citizens of other Gulf states.
The abductions were condemned by Lebanese Prime Minister Nagib Mikati and President Michel Suleiman.
“Spreading chaos in the country will not bring about the liberation of hostages. On the contrary, chaos could cause [the hostages] harm and threatens the sovereignty of the state,” the president said.
Like Syria’s other neighbors – Turkey, Iraq and Jordan – Lebanon has absorbed thousands of refugees fleeing from the conflict.
But unlike the other countries, Lebanon risks being plunged into sectarian strife, possibly even a return to civil war, by the strains inflicted on its own delicate internal situation by the Syrian crisis, correspondents say.
Last week, former information minister Michel Samaha was arrested and accused along with two Syrian military figures of plotting to destabilize Lebanon and incite sectarian fighting.
Tripoli – Lebanon’s second city – has recently witnessed street gun battles between supporters and opponents of President Bashar al-Assad.