Hezbollah "confirms that it did not take part in any clash and did not open fire in today's events until now", it said in a statement.

"All that the enemy's media is claiming about thwarting an infiltration operation from Lebanon into occupied Palestine... is completely false."

It said no Hezbollah fighters were killed or wounded.

The Israeli army said a group of three to five men armed with rifles crossed the UN-demarcated Blue Line border in the disputed Mount Dov area, claimed by Lebanon, Syria and Israel.

It said the "terrorists" had fled back to Lebanon after an exchange of gunfire and that Israeli forces had fired artillery into Lebanon "for defensive purposes".

An AFP correspondent reported Israeli bombardment of the Kfarchouba hills in the Shebaa Farms sector near the Israeli position of Roueysaat al-Alam, with plumes of smoke rising above the area.

The bombardment hit a civilian home in the village of Hibariyyeh close to the border, according to Lebanese media.

The latest spike in tensions follows a July 20 Israeli missile attack on positions of Syrian regime forces and their allies south of Damascus that left five dead.

Hezbollah, whose fighters back the Damascus regime in war-torn Syria, said one of its own was among the dead.

"Our response to the killing of... Ali Kamil Mohsen in the Zionist aggression near Damascus airport is definitely coming," the Shiite movement said in its statement.

"We will not remain quiet in the face of this day's bombardments... and the hitting of a civilian's house," it added.