Three Lebanese soldiers were killed by unidentified gunmen at a checkpoint near the Syrian border Tuesday.
The gunmen then fled into Syrian territory, a Lebanese security source said.
“The incident took place on the outskirts of Arsal and some residents pursued the vehicle that opened fire at the checkpoint before it entered Syria,” municipal chief Ali al-Hujairi said.
“We believe someone is trying to create tension between the Lebanese army and the people of Arsal,” he said.
There was no immediate claim of responsibility.
Arsal residents are predominantly Sunni Muslims who support the rebels in Syria.
The incident came as tension increased in Lebanon between Sunni supporters of the Syrian insurgency and the mainly Shiite movement Hezbollah that is fighting alongside government troops in Syria.
On Sunday, two rockets hit a mainly Shiite Muslim district of southern Beirut, wounding five people, a day after Hezbollah leader Hassan Nasrallah said his group would continue fighting in Syria.