By Erika Solomon.

BEIRUT | Fri Dec 2, 2011.

(Reuters) - Some fear walking down main streets. Some go into hiding. For many Syrian activists who have fled across the border, Lebanon is an uneasy refuge.

"You always worry that you're still in reach of the hands of the Syrian regime," said one activist, whispering in the corner of a busy coffee shop in Beirut. "Being on the other side of the border doesn't mean much."

Syria denies it, and it is impossible to prove, but many activists who have fled to Lebanon blame a series of kidnappings and reported beatings on Syrian supporters here. Some suspect Damascus itself, trying to quell an eight-month revolt against President Bashar al-Assad's rule.

Syria has a history of intervening in Lebanon, where it kept a force of up to 40,000 troops until 2005. Today its ally Hezbollah -- a Shi'ite political movement as well as a guerrilla army -- and political partners hold the majority in Lebanon's government.

Since the beginning of the protests, which Damascus blames on foreign-backed "terrorists," the Lebanese Institute for Democracy and Human Rights (LIDHR) says it has documented 13 kidnappings of Syrian activists in Lebanon.

"We receive so many reports, but for most we don't have enough information to document them," said the group's president, Nabil Halabi. "From the beginning of the protests until September 20, we estimate there were around 20 kidnappings."

Human Rights Watch says among a sea of rumors, it has only been able to document two high-profile incidents.

One is the May abduction of 89-year-old Shibli al-Aissami, a founder of Syria's ruling Baath party who became a dissident and went into exile decades ago.

One witness said Aissami was dragged into a black SUV while taking a walk in his daughter's upscale neighborhood, perched in the mountains overlooking Beirut.

"It didn't even occur to us at first that Syrian intelligence was behind it," daughter Raja Sharafeddine told Reuters in an interview. "He's an old man who had left politics -- what is there to scare or hurt them?"

LEBANESE ROLE?

Sharafeddine said it took weeks to find out how her father disappeared. A local resident said he saw the kidnapping but was too afraid to step forward right away. A diplomatic source told her that Aissami was taken to Syria.

She blames Lebanese security forces for reacting slowly.

"Either they knew from the beginning and they didn't want to say, or there was political pressure from the Syrians."

Another widely documented case was the kidnapping of three Syrian brothers from the Jassim family. The Jassims were picked up by black SUVs after one brother was released from a brief detainment after passing out fliers for an anti-Assad rally.

The government in Beirut has been largely silent on the issue, but local media in Lebanon have published leaked reports that the head of Internal Security Forces, Ashraf Rifi, told a closed cabinet meeting that Lebanese security forces working at the Syrian embassy were responsible for the four kidnappings.

Rifi has been quoted in local media saying an investigation has been launched.

"No incident will remain out of reach of investigations by the Internal Security Forces," Rifi told the Daily Star.

A security source who declined to be named said the reports were accurate and confirmed the ISF was investigating.

LIDHR's Halabi said one of the Jassim brothers was already dead: "He died of torture in a Syrian jail."

Human Rights Watch could not confirm the death, but said Lebanon must do more to prevent and investigate kidnappings.

"There's sort of a culture of impunity, not just when it relates to Syria, but any political issue in the country," said HRW's Nadim Houry in Beirut. "There is a sense that the Lebanese state is unable, or unwilling, to provide security."

Witnesses told Reuters that gunmen in three cars last week tried to abduct a Syrian worker in the border town of Arsal, but residents attacked the men and burned their cars.

The man has since disappeared from Arsal. Neighbors say he went into hiding with Syrian relatives.

TRYING TO DISAPPEAR

Even Lebanon's capital Beirut, one of the Arab world's most open and vibrant cities, is not safe for some. The city has become a self-made prison for prominent Syrian activist Omar Idlibi.

Idlibi says he gets death threats sent to him via relatives. He used to give television interviews, but now he increasingly avoids leaving his apartment for routine activities. His groceries are bought by friends.

"Lots of people try to disappear. I'm one of them. I try as much as possible not to be seen," he said.

A picture of Assad hangs above the battered couch where he sits all day coordinating with activists by phone and the Internet.

"Wanted: Dead or Alive," it reads.

"I've been here five months, but I don't know what Beirut looks like. I've put myself under house arrest," he laughs.

Even activists living more openly are loathe to wander near parts of the fashionable Beirut district Hamra. That's where the Syrian embassy and Lebanon's pro-Assad Syrian Social Nationalist Party are located.

"I'm never comfortable there, and I'm frightened of going near Makdassi street (where the embassy is)," said the activist who declined to be named.

Makdassi Street has lots of trendy bars and restaurants. It also has men in dark leather jackets whom activists accuse of attacking pro-opposition rallies outside the Syrian embassy.

At one protest, activists say a few people were beaten to the point of broken bones on the doorsteps of nearby restaurants.

"We have been profiled and threatened with further violence if we enter 'their area'..." one activist wrote anonymously for the blog Jaddiliya. "Hamra is not a safe place for those who are conscientious, progressive and politically active."

Yet Lebanon itself remains an important safe haven. Its mountainous northern border regions, long used as smuggling routes for petrol and other contraband, are now exploited to sneak people and supplies across the border.

For Idlibi, coming here was a last resort.

"My town is close to the border, and I'd never have made it to Turkey. There would be dozens of checkpoints to pass and I'd have been arrested," he said.

"I didn't want to come here ... If I could have gone anywhere, I would not have chosen Lebanon."