Gunmen have killed four people in eastern Lebanon, including two soldiers, after clashes erupted following the arrest of a Syrian accused of belonging to a jihadist group.

Saturday's fighting prompted the Lebanese army to issue a statement pledging "decisive and firm" action to prevent the Syrian conflict from spilling over into Lebanon, Reuters news agency reported.

Fighters temporarily gained control of a police station in the town, killing two soldiers and two civilians before the army recaptured the building, security sources and state media said.

The violence began after troops detained Imad Ahmed Jumaa, a Syrian man accused of belonging to al-Qaeda's Syrian affiliate, al-Nusra Front.

The army said in a statement that it had detained Jumaa at noon, and security sources and local residents said unidentified gunmen began to surround local army checkpoints shortly afterwards.

Two Lebanese civilians were killed when they tried to prevent fighters from al-Nusra Front from storming the security building in the town of Arsal, security sources and state media said.

NNA said that soldiers were killed in attacks on checkpoints, and the army acknowledged "deaths and injuries" among its ranks, but without giving further details.

Two soldiers were kidnapped earlier at the Wadi Hmeid post, but were later freed by the army.

Army stands 'firm'

Arsal, a Sunni town where tens of thousands of Syrian refugees have fled to escape fighting across the mountainous border, has seen frequent spillover from Syria and has been a tinder box for domestic tensions in Lebanon.

Syrian warplanes have bombed the town's environs and rebel fighters often cross the porous frontier, sometimes resting or seeking medical treatment in Arsal.

In a statement, the army warned of the seriousness of the situation in Arsal.

"The army will not allow any party to transfer the battle from Syria to its [Lebanon's] territory," it said.

"The army will be decisive and firm in its response and will not remain silent as foreigners try to turn our land into a field for crime and terrorism, murder and kidnapping."

In other violence on Saturday, just across the border in Syria's Qalamoun region, the forces of President Bashar al-Assad killed at least 50 rebels, including from the Nusra Front.

Source: Agencies