Sheik Hassan Nasrallah also pledged to double the number of Hezbollah fighters in neighboring Syria.
Worst attack yet on Lebanese over Hezbollah's role in Syrian civil war.
Militants accused the teenagers of being pro-government gunmen.
Follows weeks of clashes in predominantly Kurdish parts of northeastern Syria.
Syria, missle defense, human rights, and other issues divide the former cold warriors.
Road had been thought to be a secret to the Assad regime, which called the dead terrorists.
Deprives regime forces of one of their main posts near the Turkish border.
Rebel forces captured four Alawite villages in an Assad stronghold.
The Syrian military is firing ballistic missiles into populated areas; more than two hundred dead in nine attacks, Human Rights Watch claims.
The development is a major blow to beleaguered opposition forces.
