The youngest son of the late Al Qaeda leader Osama bin Laden is encouraging his fellow jihadists to "free" the holy city of Jerusalem, which he likened to a "bride," news reports say, citing the U.S. terrorist-tracking organisation SITE.

"Jerusalem is a bride whose blood is our dowry,'' Hamza bin Laden purportedly said in the online message quoted by SITE, Newsmax reports.

"The fight to free Jerusalem is a battle between faith and unbelief that requires the unity of the Umma (the Muslim community),'' he added.

Hamza, whose father and brother died in a 2011 U.S. raid, said the battle in Syria will also pave the way to freeing Palestine. "The liberation of Palestinian land has been brought much closer by the Syrian revolution.''

His message was released a week after Al-Qaeda leader Ayman al-Zawahiri also issued a message urging rival militant groups in Syria to unite or risk death.

Zawahiri reportedly expressed his support to the Al-Qaeda-affiliated Al Nusra Front's plan to create a sovereign state in Syria that would rival the self-declared caliphate of the Islamic State (ISIS).

"The matter of unity today is one of life and death,'' he said, according to The Guardian. "Either you unite to live as Muslims with dignity, or you bicker and separate and so are eaten one by one.''

Born in Egypt, Zawahiri became Al-Qaeda's leader in June 2011 just weeks after the older bin Laden was killed in a raid on his compound in Pakistan by U.S. special forces. It is believed that Hamza bin Laden managed to escape from the compound during the raid by U.S. Navy Seals.

Last August, the terror network also released an audio message purportedly from Hamza bin Laden calling for jihad against America and its allies. It mentioned in particular London, Washington, Paris and Tel Aviv as targets for attacks, Statesman.com reports.

"The Islamic Umma should focus on jihad in al-Sham (Syria)... and unite the ranks of mujahideen there,'' Hamza was quoted as saying. "There is no longer an excuse for those who insist on division and disputes now that the whole world has mobilised against Muslims.''

In another audio message discovered by Jihad and Terrorism Threat Monitor of the Middle East Media Research Institute (MEMRI), Osama bin Laden's son reportedly praised the attacks by Palestinians against Israelis, and called on Muslims around the world to kill the Jews and attack the interests of U.S. and other Western countries, the Inquisitr reports.

The young bin Laden said the supporters of the Jews "must pay the bill in their blood'' and ultimately "feel the pain Palestinians in Gaza have been experiencing.''

MEMRI noted that the young bin Laden wants to create a massive army based in Syria to free Palestine.