BEIRUT (Reuters) - Tit-for-tat kidnappings by Syrian rebels and Lebanese Shi'ite gunmen have escalated tensions in Lebanon, where the specter of contagion from Syria's conflict is alarming the fractured and war-scarred Mediterranean nation.
Despite government efforts to insulate it from turmoil in its once dominating neighbor, Lebanon has seen armed clashes in its two largest cities, and last week authorities said they uncovered a Syrian plot to destabilize the country.
The sight of masked gunmen in Beirut on Wednesday claiming the capture of 20 Syrians, and the kidnapping in broad daylight of a Turkish businessman near the airport, was another dramatic sign of Syria's crisis spilling over into Lebanon.
While they may not herald an imminent slide towards conflict in Lebanon, the incidents highlight the weak and tenuous authority of Lebanon's state institutions and point to future instability in the country of four million.
"This will have a negative impact on state authority, the military and the business environment in Lebanon" said Ayham Kamel of the Eurasia Group consultancy. "The likelihood of civil war right now remains low, but reaching this stage is a very alarming development".
To the outside world, kidnapping foreigners was a defining feature of Lebanon's civil war, and the brazen public appearance by the masked gunmen this week - unchallenged by security forces - echoed the chaos of the 1975-1990 conflict.
"This ...brings us back to the days of the painful war, a page that Lebanese citizens have been trying to turn," said Prime Minister Najib Mikati, whose policy of 'dissociation' from Syria's conflict next door has come under growing strain.
Mikati, a Sunni Muslim, heads a government in which Shi'ite Muslim militant movement Hezbollah and its Shi'ite and Christian allies - all supporters of Assad - hold half the cabinet seats.
Hezbollah, the only Lebanese armed faction not to disarm after the civil war, is the most powerful fighting force in the country. Its opponents have repeatedly and unsuccessfully called for it to put its mighty arsenal under state control.
Those long-standing sectarian tensions have been re-ignited by the mainly Sunni Muslim revolt in Syria against Hezbollah's ally President Bashar al-Assad, whose Alawite community is an offshoot of Shi'ite Islam. Shi'ite Iran, a rival to Sunni Arab powers like Saudi Arabia, sponsors both Hezbollah and Assad.
Most of Hezbollah's opponents, including Mikati's fellow Sunnis, are solidly behind the Syrian rebellion. In Sunni Muslim border areas of northern Lebanon and the Bekaa Valley, arms have been smuggled to the rebels since the start of the uprising.
Tensions over Syria led to deadly street clashes three months ago in the mainly Sunni northern city of Tripoli, home also to a staunchly pro-Assad Lebanese Alawite minority.
The kidnapping of 11 Lebanese Shi'ites in northern Syria in May also triggered street protests in Beirut.
Five days ago Lebanese authorities issued an indictment against a top Syrian security official and a former Lebanese minister whom it accused of forming an 'armed gang' that planned to detonate bombs to incite sectarian fighting in Lebanon.
Assad's woes have already emboldened some of his opponents in Lebanon, and Sunni Muslims might seek to press home political advantages against a weakened Hezbollah if he were to fall.
But analysts say that all sides in a potential Lebanese conflict know they have much to lose from all-out confrontation, an awareness which has helped them step back from the brink during several political showdowns in recent years.
Notable among such crises was the assassination in 2005 of Prime Minister Rafik Hariri and its aftermath. The still officially unsolved killing of the Sunni billionaire with close ties to Saudi Arabia saw suspicion fall on Hezbollah and Syria.
A major escalation of violence now would be likely to draw in Gulf Arab countries, strong supporters of Lebanon's Sunnis, against Hezbollah. Israel, which fought an inconclusive war with Hezbollah in 2006, could also get sucked into such a conflict.
Faced with that prospect, Lebanon's divided political leaders appear keen to avoid escalating friction.
"All the evidence of the last seven or eight years has been that all the parties in Lebanon will do all they can to prevent the country shifting into all-out civil war," said Beirut-based political commentator Rami Khouri.
Still, this week's kidnappings by a group apparently beyond the control not only of the state but also the main political leaders on its own side of the divide, serve as a warning that street violence can build a momentum of its own.
"The Lebanese state is not a powerful centralized state," Khouri said. "You have people outside the control of the state, whether it's Hezbollah or small groups like these family-based militias that operate in society.
"The worry is that these incidents can escalate and get out of hand. Then you end up with armed conflict in the street."
Editing by Alastair Macdonald