Lebanese troops raided a Syrian refugee camp in a restive border town on Thursday, with the army saying unknown assailants torched several tents while residents accused the soldiers of setting them ablaze.

In a statement, the army said its forces were carrying out raids in one refugee camp in Arsal, in eastern Lebanon, when unknown attackers tried to set fire to tents in a neighbouring camp.

"Three attackers on a motorbike attempted to set fire to the other camp, so army forces opened fire on them, killing one and wounding the others," the army said in a statement.

The statement gave no further details about the fire, but activists and others circulated photos on social media showing thick black smoke rising from a destroyed campsite in the area.

Local residents, including an official who spoke on condition of anonymity, disputed the army's story.

"Troops poured gasoline on the tents and then set fire to the camp," he told AFP. "They attacked the women and children, and rounded up the men. They detained hundreds of men."

"I was just there, and I saw an old man, around 90 years old, with all his bones broken from the beatings," he added. "There is no safety for the refugees in Arsal at all."

An army spokesperson said the local residents' stories were "lies" and repeated the details of the military's statement.

"Our troops act in accordance with international standards of humanitarian treatment," the spokesperson told reporters.

The UN's refugee agency UNHCR had no comment.

Local residents said refugees staged a demonstration to protest the incident, while activists expressed their outrage on Twitter:

Awful reports from Syrian refugee camp in Arsal today: Leb army & Hezbollah burning tents, arresting/beating/humiliating refugees. #Lebanon — James Wright (@JamesWr60729527) September 25, 2014

Though some welcomed the move:

Lebanon's official National News Agency said "dozens" of Lebanese and Syrian citizens were arrested in the raids that began in the early hours of Thursday morning.

Among them, the agency reported, were four gunmen from al-Qaeda's Syrian affiliate al-Nusra Front.

Tensions have been running high in Arsal since an incursion into the eastern Lebanese town on the border with Syria by militants last month.

Clashes broke out between militants coming from Syria and the Lebanese army, with the militants taking hostage several dozen soldiers and policemen from the town when they withdrew after a truce.

Negotiations to free the men have gone nowhere.

Militants have executed three of the hostages, causing deep anger and anxiety in Lebanon and leading to a backlash against Syrian refugees in some places.

Aid groups working with refugees say there has been an increase in attacks on Syrians, and the army has recently been forced to distance itself from soldiers shown in a video kicking and beating Syrian men, including an amputee.

There are more than 1.1 million Syrian refugees in Lebanon, which has just four million citizens.