The message was released by the Global Islamic Media Front, an al-Qaeda mouthpiece which distributes statements by the international terror organization's leaders and field commanders.
"Sons of Islam, o sons of the nation of Allah and Jihad, our brothers in the Nahr el-Bared camp in Lebanon are being subjected to the flagrant aggression of the army working for treason and apostasy, the Lebanese Army," the statement said.
"(This) is a war on Islam... It is a war planned to eliminate those who think about, and act to eliminate the State of the Children of Zion. Sons of the nation Muhammad, peace be upon him, help... your brothers in Islam. They are fighting for the sake of God... They wanted a confrontation with the Zionist aggressors, and it is the duty of every Muslim to help these boys, this is one of the most important duties today," it continued.
The message said the Lebanese Army aimed "to eliminate the Islamic Jihad and the Mujahideen (holy fighters) in the backyard of Dar Al-Sham (Syria)."
It included photographs of Fatah al-Islam fighters posing with machine guns and Koran books, with one fighter holding a small child.
A similar statement was released by 'Al-Qaeda in the Levant,' based in Lebanon, accusing the Lebanese government of embarking on a "crusade."
The group blasted Lebanon for discriminating against its Palestinian inhabitants and depriving them of basic rights.
"Since the early days the abandoned camps lacked the simplest ways of life and were filthy, surrounded by barbed wire, a big prison," the statement said. "Palestinians lived as if they were wild beasts and predators, and prevented from leaving. (This is) humiliating and an insult to the people of this nation," al-Qaeda in Levant said.
'Attack American interests and Israel's borders'
On another jihadi forum, continuous updates on the exchanges of fire between the Lebanese Army and Fatah al-Islam were interspersed with calls for Sunni Muslims to join Fatah al-Islam and attack "American interests, the (UN) international forces (in southern Lebanon), and the borders of the Jewish state, the so-called state of Israel," using "assassinations and martyrdom operations."
"We must ambush and raid, position ourselves, and carry out strikes in solidarity with our brothers in Fatah al-Islam and the (Palestinian) camp, and stand in solidarity with the people of Iraq and Palestine," one message read.
It called on Sunni jihad fighters to hit back against the Lebanese military and "switch from defense to attack through confidential, small, well-trained and highly armed units (fighting) with the doctrine of jihad."