But Interior Minister Nuhad Mashnuq said the attackers who carried out yesterday's violence had come from inside Syria, not refugee settlements nearby.
"We are worried that there are more terrorists, so the Lebanese army is searching the area," said Bashir Matar, mayor of Al-Qaa, which lies in a hilly border area shaken by violence since the civil war erupted in Syria in 2011.
Five people were killed and 15 wounded when four suicide bombers attacked the village before dawn yesterday.
Al-Qaa lies on a main road linking the Syrian town of Al-Qusayr to Lebanon's eastern Bekaa valley.
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Its 3,000 residents are predominantly Christian, but the Masharia Al-Qaa district is home to Sunni Muslims and some 30,000 Syrian refugees live in a makeshift camp on the edge of the village.
"The army has deployed a large force to Masharia Al-Qaa and is carrying out widespread searches in the displacement camps, looking for weapons or wanted people," the state National News Agency reported.
In televised comments from Al-Qaa today, the interior minister said a preliminary investigation indicated that "the suicide attackers came from Syria, not from the (refugee) tents."
"The whole village is mobilising. Everyone -- men and women -- are sitting in front of their homes to protect them after the terror that we lived yesterday," said local official Mansur Saad.
One man with silver-grey hair and clad in a black vest poured himself a small cup of coffee, his assault rifle lying in his lap.
Several women strolled through the street and posed in front of cameras, smiling and gingerly carrying weapons.
"We haven't been scared or terrified like that in our whole lives," said resident Yola Saad.
Prime Minister Tamam Salam urged residents not to take up arms and to leave the military work to the security forces.