Lebanon was battling Thursday to contain an eruption of violence triggered by events in neighbouring Syria after a spate of mass kidnappings that recalled the dark days of the country's own civil war.
Several oil-rich Gulf countries have ordered their nationals to leave the country immediately in the face of threats, particularly against Saudis and Qataris whose governments are staunch opponents of the Syrian regime.
"This brings us back to the days of the painful war, a page that Lebanese citizens have been trying to turn," Prime Minister Najib Mikati said of the 1975-90 civil war when Western hostages were seized by armed groups.
But with the government seemingly powerless to control its own streets, an armed Shiite Muslim clan claimed it had kidnapped around 20 Syrians, while many more were reportedly seized as rioters went on the rampage in Beirut.
"We are trying to resolve this issue calmly," Mikati said before an emergency cabinet meeting on the crisis.
Violence in Syria has often spilled over into Lebanon, rattling the country's already fragile security situation, with cross-border shootings, shelling by the Syrian army, tit-for-tat kidnappings and sectarian clashes.
But the latest unrest has fanned fears that the 17-month conflict in its much larger neighbour could further destabilise Lebanon, which has struggled for decades with wars, sectarian strife and a weak political system.
Already the country has had to deal with an influx of about 38,000 refugees from the conflict across the border.
The Muqdad clan claimed it kidnapped about 20 Syrians and a Turkish national after a family member was abducted this week by a Syrian rebel group which accused him of being a Hezbollah sniper.
Dozens more Syrians were seized and their shops vandalised by rioters in southern Shiite areas of Beirut on Wednesday, according to the state news agency.
The attacks erupted after unverified reports that several abducted Shiite Lebanese pilgrims were among those killed when a government war plane bombed the northern Syrian town of Aazaz.
Signup to our newsletter and follow us on Facebook and Twitter!
Lebanese President Michel Sleiman said he held talks with security leaders and other ministers to discuss the kidnappings.
"God willing, the Lebanese in Syria will be released and so will the kidnapped Syrians in Lebanon."
Shiites in Lebanon's fractured multi-confessional population mainly support President Assad's Alawite-led regime, while Sunnis back the rebellion.
Saudi Arabia, which is opposed to Assad's regime and hosted an Organisation for Islamic Cooperation summit which suspended Syria Thursday, told its citizens to leave immediately after "clear threats against them."
Washington, too, expressed consternation.
"Our concern in Lebanon, first and foremost, has been the spillover from the Syrian conflict and the fact that the sectarian tensions in Syria are potentially being replicated in Lebanon," State Department spokeswoman Victoria Nuland told reporters.
An exodus of tourists could deal a major blow to Lebanon, a favourite summer destinations for Gulf tourists seeking to escape their searing hot climate for the cooler Mediterranean climate and a much more liberal lifestyle.
Adding to the feeling of insecurity, rioters closed the road to Beirut airport and to the border with Syria on Wednesday, and an Air France was diverted because of the troubles, but the situation was calm Thursday.
But the clan involved in the kidnappings said it would not back down.
"We have our group of Free Syrian Army hostages and don't intend to take any more but if our relative Hassan is killed in Syria, the first to be executed will be the Turk," warned spokesman Maher al-Muqdad.
Arab media reports said a Syrian rebel group claimed the abduction of Hassan al-Muqdad, accusing him of being a sniper and a member of the Lebanese Shiite militia Hezbollah, an allegation denied by the clan.
In turn, an unknown group calling itself the "Vanguard of the Salafist Jihad in Lebanon," threatened the Muqdad family, saying if it failed to release the hostages "there will only be the language of weapons between us."
Syria occupied Lebanon militarily and politically for nearly three decades until 2005, when its troops were forced to pull out under international pressure after the assassination of former Lebanese premier Rafiq Hariri.