An attack on Lebanese troops raiding a Syrian refugee camp has stirred violent debate and polarised opinions, with rising calls to repatriate refugees but also warnings against racist rhetoric.
The uptick in pressure comes after Lebanese soldiers were attacked as they stormed two refugee camps near the eastern border with Syria last month.
They were confronted by a string of suicide attacks and grenade blasts that killed a child and wounded seven soldiers.
Dozens of people were arrested, and the army subsequently announced four detainees had died of pre-existing conditions, prompting rights groups to urge a probe into allegations of torture.
The incident has produced a campaign of incitement against Syrian refugees on social media, with many Lebanese pushing back and warning against stereotyping refugees as militants.
More than one million Syrian refugees have flooded into Lebanon since the conflict in their own country erupted in March 2011.
They live in homes and informal camps, and their presence has been largely tolerated, despite testing the limited resources and ageing infrastructure available to Lebanon's four million citizens.
But in the wake of the Arsal incidents, anti-refugee rhetoric has been sounded by Lebanese artists, media and high-ranking politicians, including Christian leader Samir Geagea.
He warned that if "the United Nations doesn't accept that refugees should be returned to Syria, we'll put them on the first boat back. We will not tolerate it anymore."
Foreign Minister Gebran Bassil, a member of a rival Christian party, has also stepped up his long-standing expressions of concern about the huge refugee influx.
"We warned from day one that the refugee issue was a major concern for us and it has proved correct because it has become a refuge and a shelter for some terrorists," he wrote on his Twitter account.
The official rhetoric has been accompanied by duelling social media posts, vilifying refugees or denouncing the army for alleged abuses.
The rising tempers prompted President Michel Aoun to call for calm, while acknowledging the frustrations of those who feel burdened by the refugee presence.
"Resolving the refugee crisis... will not be via disseminating and propagating hatred," he added, warning of the consequences of "the game of spreading hatred".
But even after his comments, a video has circulated showing at least three Lebanese punching and kicking an unarmed Syrian refugee and hurling insults at him.
The assailants are also heard accusing their victim of opposing the Lebanese army and of supporting the Islamic State (IS) militant group.
The video was widely criticised and Interior Minister Nuhad Mashnuq announced on Wednesday that the attackers had been arrested.
Earlier, many Lebanon social media users had been infuriated by another video showing an elderly Syrian woman insulting the Lebanese, as well as the army and politicians, over the Arsal incident.
The ugly rhetoric and charged atmosphere has brought comparisons with the debate over the presence of Palestinian refugees in the run-up to Lebanon's 1975-1990 civil war.
Hilal Khashan, a professor of political science at the American University in Beirut (AUB), said the rhetoric reflects a lack of civic education in Lebanon.
"The campaigns of incitement and obscene language are not part of a systematic plan," he told AFP.
The enormous refugee presence "is placing a major demographic burden on Lebanon and its political balance", he added.
"The refugee issue is an international issue and goes beyond Lebanon's ability to deal with it."
In the years since the civil war, Lebanon has maintained a fragile sectarian and political balance that has at times been threatened by the conflict in Syria next door.
Amid fears that many Syrians may never leave the country, Lebanon's political parties are now united in seeking a repatriation plan.
But they differ on how the process should work, with the powerful Hezbollah, an ally of President Bashar al-Assad, urging coordination with Damascus, while others propose UN supervision.
As tempers fray, the hashtag "no to racism" in Arabic has made its appearance on Twitter.
"We ask our brothers, the Syrian refugees in Lebanon, to forgive us for things that certain shameless people have committed against you," photographer Wael Ladki has tweeted.
Rima Majed, an AUB professor, warned on Facebook that a political decision has already been taken "to blow up the refugee file".
Against this already tense backdrop, preparations are underway for a major army operation against militants in Arsal.
Hezbollah chief Hassan Nasrallah last week warned that extremists in the Jurud Arsal region were "a threat to all, including the Syrian refugee camps".
"It is time to end this threat," he said.
Prime Minister Saad Hariri this week announced an operation would be forthcoming.
"The Lebanese army will carry out a planned-out operation in Jurud Arsal and the government gives it freedom (to do so)," he said.