The mysterious case of 11 Lebanese Shiites who were taken hostage in Syria last week is raising fears of renewed street battles in Beirut as Lebanon increasingly gets drawn into the swirling chaos next door.

The Syrian crisis already has spilled across the border into Lebanon over the past three weeks, sparking deadly violence in a country that remains deeply divided over the 15-month-old uprising against Syrian President Bashar Assad.

But the Shiites' abduction is potentially explosive, in part because it enflames Lebanon's fragile Sunni-Shiite fault line. It could also spark retaliatory attacks against the thousands of Syrians in Lebanon.

In recent days, members of Lebanon's powerful Shiite militant group, Hezbollah, have deployed at the entrances of Beirut's southern suburbs, a heavily Shiite area, to prevent any moves by angry protesters.

Hezbollah is a staunch ally of the Syrian regime, where a predominantly Sunni uprising is trying to oust the Assad family dynasty. The families of the kidnapped Shiites blame Syria's Sunni rebels for abducting the men.

"The kidnapping is clearly intended to drag Hezbollah into the Syrian quagmire," said Ziad Baalbaki, a 37-year-old Lebanese insurance broker in Beirut. "The whole thing is fishy, everyone is worried what will happen if they are not released or they turn out to be dead."

The Lebanese men were on their way back from a pilgrimage in Iran on May 22 when gunmen intercepted their buses in the northern Syrian province of Aleppo, according to the women on the pilgrimage who were allowed to go free and arrived in Lebanon hours later.

Since then, no one has claimed responsibility for the kidnapping. There were reports Friday that the hostages were about to be released, prompting a rush on the airport by family members. But the men never arrived, and it became clear the release plans went awry.

One opposition figure who said he spoke to the kidnappers told The Associated Press that the hostage takers decided not to release the men after Syrian forces began attacking rebel areas in Aleppo. Now, he said, the kidnappers are demanding Syrian authorities release 500 opposition detainees, including Lt. Col. Hussein Harmoush, one of the first officers to defect after the uprising began. Harmoush was later arrested by authorities during a special operation.

The opposition figure spoke on condition of anonymity for fear of reprisals.

Lebanese officials and Syrian activists have said the men are being held in an area near the Turkish border, but there is little credible information about their fate. Shiite leaders in Lebanon have scrambled to deny various rumors that might aggravate the situation — including reports that one of the hostages is related to Hezbollah leader Sheik Hassan Nasrallah.

"The information indicates that they are alive and in good health. This is what the Syrian opposition and Turkish officials confirm," Parliament Speaker Nabih Berri told An-Nahar daily Monday.

Shortly after news of the abduction broke last Tuesday, dozens of angry protesters blocked major roads with burning tires and threatened to kidnap Syrians in Lebanon as a form of retaliation. The protesters went home only after Nasrallah went on TV, calling for calm and saying no Syrians in Lebanon should be harmed.

"They were kidnapped because they are Shiite, not for any other reason," said Mohammed Mir, a Lebanese Shiite. "Had they been returning from Haj in Saudi Arabia (a Sunni country) would anyone have dared to kidnap them?"

In the Bir el-Abed district south of Beirut on Monday, five female relatives of the kidnapped men sat silently inside the office of the religious tour agency Badr al-Kubra, which organized the pilgrimage.

The room was decorated with large posters of Iran's Supreme Leader Ayatollah Ali Khamenei, Nasrallah, and the group's late military commander Imad Mughniyeh, who was assassinated in a car bomb in Damascus in 2008.

The women refused to be interviewed, saying they were worried it would hurt the negotiations taking place for the hostages' release.

The case has the potential to inflame sectarian tensions in Lebanon and trigger retaliatory attacks against tens of thousands of Syrians nationals now in Lebanon. The overwhelming majority of rebels fighting Assad's regime are Sunni Muslims, while Assad and the ruling elite in Syria belong to the tiny Alawite sect, an offshoot of Shiite Islam.

Tensions from Syria have already spilled into Lebanon and clashes between Alawites and anti-Assad Lebanese Sunni groups in Lebanon's second largest city of Tripoli killed eight people earlier this month.

Aleppo-based activist Mohammed Saeed said the kidnappers have "impossible demands" from the regime in return for the release of the hostages, such as setting free all Aleppo province detainees and the withdrawal of the Syrian army from some areas.

"They are dealing with them (hostages) as if they are members of the regime," Saeed said.