(AP) BEIRUT – Armed Shiite clansmen in Lebanon said Wednesday they had captured more than 20 Syrians and will hold them until one of their relatives seized by rebels inside Syria is freed. The tensions were a stark reminder of how easily Syria’s civil war could spill over to neighboring states.

In Geneva, a U.N. investigation said Syrian President Bashar Assad’s forces and pro-government militiamen were responsible for war crimes during a May bloodbath in the village of Houla that killed more than 100 civilians, nearly half of them children. It also said rebels were blamed for war crimes in at least three other killings.

The report by the U.N. Human Rights Council said the scale of the Houla carnage indicated “involvement at the highest levels” of Syria’s military and government. It is first time the U.N. has described events in Syria’s civil war as war crimes and could be used in possible future prosecution against Assad or others. The council also said the conflict is moving in increasingly “brutal” directions on both sides.

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As the fighting deepens, so do the fears of it triggering unrest in fragile Lebanon, which is deeply divided between supporters and opponents of President Bashar Assad’s regime. The country, which was devastated by its own 15-year civil war that Syria was deeply involved in, has witnessed clashes between pro- and anti-Syrian groups over the past months, mostly in the northern city of Tripoli.

Syrian rebels have adopted a new tactic recently of seizing prisoners from countries or foreign groups allied with the regime to rattle Assad and his allies outside the country. In May, Syrian rebels captured 11 Lebanese Shiites shortly after they crossed from Turkey on their way to Lebanon. Earlier this month, rebels abducted 48 Iranians near the capital Damascus.

The Syrian rebels are predominantly Sunni whereas Assad and his inner circle are dominated by Alawites, an offshoot of Shiite Islam.

The Lebanese prisoner in Syria, Hassane Salim al-Mikdad, appeared in a video released by rebels over the past few days. He said he is a member of Hezbollah, the Lebanese Shiite militant group allied with predominantly Shiite Iran and with Syria. The captive, who appeared to have bruises on his face, said he was sent to Syria to fight with Assad regime forces.

Hezbollah denied al-Mikdad is a member and his family claimed he has been living in Syria for more than a year.

Abu Ali al-Mikdad, a relative, told reporters in Beirut Wednesday that his Shiite clan has abducted “more than 20 Syrians” including a senior member of the rebel Free Syrian Army (FSA). Later, the clan said it also had seized a Turkish man, and Lebanese state TV displayed a Turkish passport provided by the al-Mikdad family. Turkey is a strong backer of the Syrian rebels.

The Beirut-based TV station Al-Mayadeen aired a video purporting to show two of the abducted Syrians who said they are members of the FSA. One of them identified himself as Capt. Mohammed and said his job was to supply the FSA with arms and fighters.

“I call them (FSA) upon to free the prisoners they are holding because they are innocent,” said one of the two captured men shown on TV who identified himself as Maher Hassan Rabih.

The al-Mikdad family is a powerful Shiite Muslim clan that originally comes from the eastern Bekaa Valley, an area where state control is somewhat tenuous. Like most tribes in this area, they have their own armed elements.

Activists reported shelling and clashes in the northern city of Aleppo, Syria’s largest, where rebels took over several neighborhoods over the past weeks. The Britain-based Syrian Observatory for Human Rights said the rebels were trying to take over a key dam in the northern town of Manbij, just east of Aleppo.

It added that the army was using helicopter gunships in the battles near the dam on the strategic Euphrates River. In the northern town of Azaz – where the 11 Lebanese had been held – at least two air strikes leveled dozens of buildings. Att least eight people were killed, including a baby. Activists drove some of the dozens of wounded to the nearby Turkish border for treatment.

Some rescuers brought a generator and electric saw to cut through steel reinforcement bars in the concrete. Nearby, a woman sat on a pile of bricks that was once her home, cradling a baby.

U.S.-based Human Rights Watch said Syrian government fighter planes fired rockets that struck the main emergency hospital in an opposition-controlled area of Aleppo a day earlier, wounding two civilians and causing significant damage. Human Rights Watch said its members visited the damaged hospital.

The Local Coordination Committees, another activist group said there was also fighting near a border crossing with Turkey that the rebels had captured last month. A local official in the Turkish border town of Reyhanli said clashes could be heard coming from the region on Tuesday but that the situation had calmed by Wednesday morning. The official spoke on condition of anonymity because he was not authorized to talk to the media.

Turkey’s state-run Anadolu news agency said 757 Syrians fled their country and streamed into Turkey on Wednesday.

Activists say more than 20,000 people have been killed since the start of Syria’s revolt, inspired by other Arab Spring uprisings against autocratic regimes in the region. The conflict has slowly morphed into a full blown civil war.

The LCC reported violence in the eastern province of Deir el-Zour, northwestern region of Idlib, Daraa to the south and in suburbs of the capital Damascus.

In Damascus, a bomb attached to a fuel truck exploded Wednesday outside a hotel where U.N. observers are staying, 양주출장샵 wounding at least three people, Syrian state TV reported. Activists also reported clashes in different parts of Syria, including clashes with rebels near the government headquarters and the Iranian embassy both in Damascus.

Deputy Foreign Minister Faisal Mekdad toured the area of the blast and said none of the U.N. staff was hurt. The explosion occurred as U.N. humanitarian chief Valerie Amos was in the Syrian capital but her team is believed to be staying at a different hotel.

The blast was the latest in a series of explosions that have hit Damascus in the past months as clashes between government troops and rebels reached the capital, which had been relatively quiet since the uprising against Assad erupted in March last year.

Wednesday’s explosion went off about 300 yards from the military command. According to an Associated Press reporter at the scene, the blast was inside the parking lot of a military compound. The lot is near the Dama Rose Hotel, popular with the U.N. observers in Syria and where many of the mission staff are staying.

It was not immediately clear who was behind Wednesday’s explosion or what was the intended target. There have been several high-profile bombings in the Syrian capital. On July 18, an explosion in a key government headquarters in Damascus killed four top generals, including Assad’s brother-in-law. And in March, a double suicide bombing in Damascus killed 27 people.

“Those who carry out such terrorist attacks are destroying their country in order to get some pounds,” shouted a Damascus resident, Ali Mohammed Ismail, 48, who said he happened to be in the area when the explosion went off.