Saudi Arabia and the United Arab Emirates on Wednesday told their citizens in Lebanon to leave urgently, citing threats of kidnapping by armed groups angry over rebels in Syria taking prisoners from Lebanon and Iran.

Armed Shiite clansmen in Lebanon say they have taken 20 Syrians hostages until their relative seized by rebels in Syria is freed. Syria rebels claim to be holding a Lebanese man they accuse of being a member of Hezbollah, the Shiite Lebanese group allied with Syria and Iran.

Dozens of Syrian-owned shops were also vandalized in Beirut on Wednesday, reports said.

A statement by the Saudi Embassy in Beirut published on the official Saudi Press Agency and Lebanon’s National News Agency told citizens to leave immediately and warned travelers against visiting Lebanon, a popular destination for Gulf residents in the summer.

The UAE issued a similar warning, with Foreign Minister Sheikh Abdullah bin Zayed Al-Nahayan tweeting: “Unfortunately, the situation is very dangerous.”

The violence erupted on the streets of Beirut after unconfirmed reports that several Lebanese Shiite pilgrims who were taken hostage in Syria in May had been killed.

Rioters have also cut off the road leading to Beirut international airport, setting fire to tires, while an Air France flight was forced to divert to Amman because of the insecurity.

One rioter at the roadblocks issued a warning against Qataris and Saudis, an AFP journalist said.

The spokesman of a Shiite Lebanese clan said it had kidnapped 33 Syrians in Beirut and the eastern Bekaa valley, including a rebel Free Syrian Army captain who was being treated for an injury in a hospital.

It also kidnapped a Turkish man, spokesman Hatem Al-Muqdad, adding that the abductions were “to demand the liberation of our 40-year-old relative Hassan, who was kidnapped in Syria yesterday.”

“Tomorrow the number may rise to 50, because it is the only way to save the life of Hassan,” he said. “And those who ordered his kidnapping will pay dearly.”

Conflict in neighboring Syria has often spilled over into Lebanon with cross-border shootings, shelling by the Syrian army, tit-for-tat kidnappings and sectarian clashes between groups which are divided over the revolt.

Lebanon’s sectarian make-up has Shiites mainly supporting Assad’s regime, and Sunnis supporting the insurgents.

Dozens of other Syrians were also kidnapped in a southern suburb of Beirut, according to NNA, after unverified reports were broadcast claiming several Lebanese kidnapped in Syria in May were killed in an air strike in the northern town of Aazaz on Wednesday.

According to the Syrian Observatory for Human Rights, seven of the 11 Lebanese Shiite pilgrims were wounded, but none was killed.

“The relatives and neighbors of several Lebanese kidnapped in Syria took to the streets, and started to harass Syrians and vandalize their property in the area,” the NNA said.

“Some of the attackers vandalized shops, destroyed cars for sale, and kidnapped dozens of Syrians,” it said. “The situation has got out of control.”

Syria’s main opposition coalition condemned the kidnappings, as Syrians seeking refuge in Lebanon from violence in their country expressed fears over Thursday’s incidents.

“The Syrian National Council expresses its deep dismay at the kidnapping of a large number of Syrian citizens, who had fled to Lebanon to take refuge from bloody oppression in their country,” it said in a statement.

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 that year.

Seven years after Syria withdrew from Lebanon, the country’s political forces remain sharply divided over events in their neighbor.

The clan spokesman said he refused to negotiate with any party, except with the International Committee of the Red Cross or the Lebanese army chief, about the release of his hostages.

According to a pan-Arab television station, a Syrian rebel group claimed responsibility for the abduction of Hassan Al-Muqdad, accusing him of being a sniper and a member of Lebanese Shiite militia Hezbollah, which supports Assad’s regime.

“He is neither a sniper nor a member of Hezbollah,” said Abu Ali, also a member of the Muqdad clan. “All the accusations are a lie. Our request is not political, this is a humanitarian issue.”