The village of Qaa was targeted on Monday in two waves of suicide attacks that killed five people. The first group of bombers attacked before dawn and the second later at night, two of them blowing themselves up near a church.
Security officials believe Islamic State militants were behind the attack. There has been no claim of responsibility.
In reference to the number of attackers, the Lebanese government said the attack and the "unfamiliar way" it was carried out represented a new phase of "confrontation between the Lebanese state and evil terrorism".
Prime Minister Tammam Salam "expressed his fear that what happened in Qaa is the start f a new wave of terrorist operations in different areas of Lebanon," Information Minister Ramzi Jreij said in televised comments after a cabinet meeting.
Sunni Islamist militants have repeatedly struck in Lebanon since the eruption of the war in neighbouring Syria, where the powerful Lebanese Shi'ite group Hezbollah is fighting in support of President Bashar al-Assad.
Interior Minister Nohad Machnouk, speaking from Qaa, said most of the attackers had come from inside Syria, and not refugee camps hosting Syrian refugees who number well over 1 million in Lebanon.Local authorities had imposed curfews on Syrian refugees in the area following the attacks.