At least 20 Syrian refugees were killed and 400 more were arrested when the Lebanese army raided two refugee camps in the Arsal area at the border with Syria on Friday, local reporter said.
The raids were part of a major security sweep by the army in an area that has been a flashpoint for violent spillover from the Syria crisis, and several Islamic State officials were among some 350 people detained, a security source told Reuters.
Five suicide bombers attacked Lebanese soldiers as they raided two Syrian refugee camps and a sixth militant threw a hand grenade at a patrol, the army said.
The army said seven soldiers were wounded and a girl was killed after one of the suicide bombers blew himself up in the midst of a family of refugees. It did not elaborate.
The Lebanese army has in recent months stepped up raids in the makeshift camps built on the edge of Arsal, where refugees live in squalid conditions.
The manhunt inside the sprawling camps on the border area came after intelligence reports that militants were preparing to stage a series of attacks inside Lebanon.
The camps around the town have long been a haven for militants coming from Syria who have clashed with Lebanese forces conducting security raids searching for suspects hiding among the refugees.
A Lebanese army statement said one suicide bomber had detonated his explosive laden belt in front of an army patrol during a manhunt for suspected militants in a refugee camp in the northeastern border town. Three soldiers were wounded.
The army said four other suicide bombers blew themselves up without causing any injuries among soldiers, while another militant threw a grenade at a patrol, wounding four soldiers.
During the raids an explosive device blew up while four other explosive devices were defused, it said.
The defense minister was quoted as saying the incident showed the importance of tackling the refugee crisis - Lebanon is hosting over 1 million refugees - and vindicated a policy of "pre-emptive strikes" against militant sleeper cells.
Lebanese militant group Hezbollah, which backs Bashar al Assad in his fight against Syrian rebels, said the raids complemented its own fighters' campaign to stop militants entering Lebanon from Syria.
"What is needed today is to unify efforts more and more to fill all the gaps that terrorists can infiltrate from to protect Lebanon and its people from the big dangers that target it," the Hezbollah statement said.
There has been frequent fighting between the army and militants dug into the hills around Arsal in a large pocket of territory straddling the border.
The U.N. refugee agency says Lebanon hosts more than 1 million registered Syrian refugees - constituting a quarter of its population.
The government puts the number at 1.5 million. They are scattered across the country in informal tented settlements where many face the risk of arrest due to lack of legal residency that they struggle to obtain
