Four rockets fired from Syria hit the Hezbollah-dominated Bekaa Valley in eastern Lebanon Monday, wounding one person, the Lebanese army said.
Hezbollah, a powerful Lebanese Shiite movement, has come under repeated attack by Sunni extremists incensed over its intervention in Syria on behalf of President Bashar al-Assad's regime, which is battling a Sunni-led rebellion.
"At around 1:30 pm (1130 GMT) today, a rocket landed in Labweh village and three others hit the area surrounding the villages of Labweh and Al-Nabi Othman," the army said, adding that the source of the fire was "from the Syrian side" of the border.
Meanwhile, clashes broke out in the northern Lebanese city of Tripoli between supporters and opponents of the Assad regime, with one Syrian man killed in the Sunni Bab al-Tabbaneh neighbourhood, a security source said.
Residents of Jebel Mohsen, who belong to the same Alawite offshoot of Shiite Islam as the Assad family, frequently clash with groups in Bab al-Tabbaneh, a Sunni neighbourhood supportive of the rebels.
The violence came a day after two Hezbollah members, including a local official, were killed and 14 others wounded in a suicide car bomb attack in Al-Nabi Othman, according to the official National News Agency.
"The blast was carried out by a suicide attacker. Hezbollah members knew he was about to carry out the attack, and tried to stop the vehicle. That was when the attacker detonated the vehicle," a security source said.
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The attack was claimed by the jihadist Al-Nusra Front in Lebanon and by a little known group, Liwa Ahrar al-Sunna in Bekaa, as revenge for Hezbollah's military involvement in Syria.
Hezbollah has sent thousands of fighters to support Assad's troops and helped in the capture of Yabrud, a key Syrian rebel bastion near the border with Lebanon.
Hezbollah-dominated areas in eastern Lebanon and southern Beirut have suffered a series of deadly attacks, many of them suicide car blasts, since the movement acknowledged sending fighters into Syria.
On Monday the army detonated a car parked on a dirt road that was apparently being prepared for a fresh attack.
According to a security source, troops fired at the vehicle, parked some 300 metres (yards) from a school, causing a powerful explosion.
Lebanon is sharply divided over the conflict in neighbouring Syria, which dominated the small Mediterranean country for nearly 30 years until 2005.
While Hezbollah and its allies support Assad, Lebanon's Sunni-led opposition favours the revolt.
Hundreds of people have been killed in Syria-related bomb attacks and clashes in Lebanon since the start of the uprising in March 2011.