More than a dozen rockets and mortar rounds fired from Syria struck eastern Lebanon Saturday, security officials said, as tensions rise in the two countries' borderlands where Hezbollah militants are playing a bigger role in Syria's civil war.

The Lebanese security officials said the Baalbek region was struck 16 times, igniting fires in fields but causing no casualties. They spoke on condition of anonymity because they were not authorized to brief reporters.

Syrian rebels have fired dozens of rockets on Lebanon's northeastern region of Hermel over the past weeks but Saturday's attack was the first on Baalbek, a stronghold of Hezbollah. The Lebanese group is fighting alongside Syrian President Bashar Assad's forces against rebels who aim to overthrow him.

Hezbollah's involvement in the Syrian war increased sharply in April, when the group's fighters and Syrian government forces began a major offensive to recapture Qusair, which had fallen to the rebels shortly after the uprising against Assad began in March 2011.

The officials said the villages of Yanta, Brital and Saraeen were among the areas struck Saturday.

In another development, the officials said gunmen opened fire on a Shiite shrine in Baalbek, damaging it in an attack that could worsen frictions between the country's Shiites and Sunni Muslims. The attack on the shrine of Sayida Khawla, a great granddaughter of Islam's Prophet Muhammad, occurred shortly after midnight, the official said.

Syria's civil war is increasingly spilling over into neighboring Lebanon, where clashes between fighters who back and oppose Assad have left scores dead and wounded in recent months.

Lebanon and Syria share a complex web of political and sectarian ties and rivalries that are easily enflamed. Lebanon, itself plagued by decades of strife, has been on edge since the beginning of the uprising against Assad.

Lebanon's population is deeply divided over the conflict, which began as mostly peaceful protests but later degenerated into all-out civil war. Some Lebanese Sunnis support the Syrian rebels, who are also mostly Sunni, while some Shiites back Assad's regime, dominated by his Alawite sect that is an offshoot of Shiite Islam.

Also Saturday, the Britain-based Syrian Observatory for Human Rights said that clashes between troops and Hezbollah fighters with rebels in Qusair left at least one opposition gunman dead. The group also reported fighting in the rebel-held town or Rastan, about 50 kilometers (31 miles) north of Qusair.

The regime and the opposition both value Qusair, which lies along a land corridor linking two of Assad's strongholds, the capital of Damascus and an area along the Mediterranean coast that is the heartland of the Alawite minority. For the rebels, holding the town means protecting their supply line to Lebanon, just 10 kilometers (six miles) away.

State-run Syrian TV said troops on Friday captured the village of Jawadiyeh outside Qusair, closing all entrances leading to the town and tightening the government's siege. The announcement came hours after anti-government activists said that many rebels from the northern province of Aleppo were able to enter Qusair to defend the town against advancing troops.

Syria's state-run news agency SANA said that troops discovered and destroyed a 200-meter (yards) tunnel that linked Harasta, a suburb of the capital Damascus, with the highway that links the capital with the central city of Homs.

Troops have been advancing in areas around the capital over the past weeks.

In Aleppo, Syria's largest city, the Observatory said that at least 31 detainees have been killed by rebel shelling of the city's central prison over the past two weeks. It added that the dead were buried in one of the yards in the jail.

The Observatory also said that an Islamic court in Aleppo executed the commander of the rebel Muhammad's Army Brigade and his aide after they were charged with murder, theft and taking bribes. Such sentences are not uncommon in rebel-held areas.

More than 70,000 people have died in Syria's civil war according to the U.N.