Saudi Arabia has given Lebanon's military $1bn to help its fight against self-declared jihadist fighters on the Syrian border.
The Saudi gift came as Lebanon army's chief urged France to speed up promised weapons supplies and amid reports that a group of Muslim religious leaders were trying to mediate an end to the fighting.
After fighting in the eastern area on Tuesday, where troops have been clashing with the fighters since Saturday, ambulances entered the town of Arsal amid reports of a temporary truce.
Earlier, three out of 20 police officers detained by the fighters were released, according to police sources, reportedly as part of negotiations for a ceasefire.
In-depth coverage of escalating violence across Syria
There was a brief lull in the fighting, but shelling and artillery fire resumed on Tuesday evening, an AFP correspondent said.
The Arsal violence has left 16 soldiers dead and 85 wounded, while dozens of fighters are said to have been killed, along with three civilians.
Another 22 soldiers are missing, possibly having been taken hostage.
Tensions have also risen in northern Lebanon, where clashes killed a child and wounded 11 other people, including seven soldiers.
Clashes also erupted in parts of the northern port city of Tripoli on Monday night and continued into Tuesday.
More fighting took place in the Bab el-Tebbaneh district, where Sunni fighters regularly fire on the army and their pro-Syrian regime neighbours in the Jabal Mohsen area.
A 12-year-old girl was killed in the clashes and 11 people were injured, seven of them soldiers hurt when armed men attacked their bus.
The violence in Arsal erupted on Saturday after the arrest of a Syrian man who the army said had confessed to being a member of the Nusra Front, an al-Qaeda affiliate battling Assad's forces.
Saudi Arabia's aid to 'strengthen security'
While France has said it will respond "quickly" to Lebanon's request to expedite weapons delivery, Saudi Arabia has gone further and handed Lebanon's army $1bn to strengthen security, according to Saad Hariri, former Lebanese prime minister.
Saudi King Abdullah "has informed me of his generous decision to provide the Lebanese army ... with $1bn to strengthen its capabilities to preserve Lebanon's security," Hariri announced in Jeddah early on Wednesday.
Speaking from King Abdullah's palace in the Saudi Red Sea city, Hariri - the Lebanese Sunni community's most prominent political representative - added that "we have received this aid".
"This aid is very important especially at this time when Lebanon is fighting terrorism," he said.
Saudi Arabia is already financing a $3bn package of French military equipment and arms for Lebanon's army.
The fighting in Arsal is the worst violence to hit the volatile border region since the 2011 outbreak of the armed uprising in Syria against President Bashar al-Assad.
Speaking to AFP, Lebanon's army chief General Jean Kahwaji said the military was hamstrung in its fight against the fighters.
"This battle requires equipment, material and technology that the army doesn't have," Kahwaji said.
"That's why we need to speed up the delivery of the necessary military aid by finalising the list of weapons requested from France under a Saudi-financed deal."
In December, Saudi Arabia agreed to finance the $3bn package of French military equipment and arms for Lebanon's army.
And in mid-June, at a conference in Rome, the international community pledged its backing for the Lebanese military.
Details of what arms will be provided have not yet been finalised.
France insisted on Tuesday that it stood behind the Lebanese army.
"France is fully committed to supporting the Lebanese army, a pillar of stability and unity in Lebanon," Vincent Floreani, a foreign ministry spokesman, said.
"We are in close contact with our partners to quickly meet Lebanon's needs."
Lebanon is hosting one million Syrian refugees, and despite an official policy of neutrality over the Syria conflict, it has regularly seen the fighting spill over.