Tripoli: Lebanon's army stepped up its assault on Islamic militants hiding inside a Palestinian refugee camp on Sunday, launching artillery and sending in armoured carriers and special forces.

Witnesses in the Nahr Al Bared camp reported some of the heaviest army shelling since June 1, when the Lebanese army, using tanks and artillery, launched an offensive to drive out Fatah Al Islam militants.

Security officials said five soldiers were killed and 15 wounded on Saturday, some seriously.

A senior Fatah Al Islam commander denied reports that there was a major army assault on militants inside the camp and said fighters were holding their ground against the army.

Abu Hureira, Fatah Al Islam's deputy commander, said, "We are on the front lines across from them."

Abu Hureira, whose real name is Shehab Al Qaddour, dismissed media reports that he and Fatah Al Islam leader Shaker Youssef Al Absi were wounded as "rumours". He said some fighters were "lightly" injured "but it's nothing compared to them," he said, referring to Lebanese army casualties.

Tensions in Lebanon have been high since fighting broke out May 20 between the army and Fatah Al Islam militants in Nahr Al Bared.