Lebanon's army chief General Joseph Aoun said on Friday the situation in the country was worsening and would further escalate as a financial crisis stokes political and social tensions.

"Our responsibility is large in this period and we need to preserve the security of the nation and its stability and prevent chaos," General Aoun said in a speech to army personnel posted on the army's official Twitter account.

Lebanon is in the throes of an economic meltdown that is threatening its stability and has been dubbed by the World Bank as one of the deepest depressions of modern history.

General Aoun was speaking one day after veteran Sunni politician Saad al-Hariri abandoned efforts to form a government, plunging Lebanon deeper into crisis.

After Hariri's announcement on Thursday protesters had blocked roads in predominantly Sunni areas, burning tyres and garbage with some clashes resulting in one army soldier being injured.

On Friday 15 army soldiers were injured in confrontations with protesters in Tripoli, Lebanon's poorest city. The army has long been seen as one of the few institutions in Lebanon that can rally national pride and create unity. Its split along sectarian lines at the start of Lebanon's civil war helped fuel a descent into militia rule.

"Our nation trusts us and so does the international community," General Aoun said.

"Everyone knows that the military institution is the only one that is still effective."

Aoun said the responsibility for the army was great at a time when its personnel were "living with the anxiety of providing for the basics of a good life," for their families.

Discontent has been brewing in the security forces as Lebanon's currency has lost more than 90% of its value against the dollar, driving down soldiers' wages. Many have taken extra jobs. Some have quit.

"Our nation trusts us and so does the international community," General Aoun said.

"Everyone knows that the military institution is the only one that is still effective."