In the video telecast on Friday, Ayman al-Zawahiri said addressing Muslims in general: "I call upon them to reject any referendum on Palestine, because Palestine is not for bargaining or bidding.
"Palestine was a land of Islam, and its liberation is the duty of every Muslim."
Mentioning armed Muslim fighters, prisoners and their families, al-Zawahiri said: "I call upon Muslims everywhere to support the brothers in Palestine."
But he did not mention Hamas by name, which too opposes the referendum proposed by Mahmoud Abbas, the Palestinian president, as he did in an earlier tape when he criticised the Palestinian Islamic movement for participating in elections.
Al-Zawahiri criticised the Arab peace initiative and blamed George W Bush, the US president, for the Palestinian people's financial hardships.
"The Arab leaders didn't have the courage ... to meet the Palestinians needs for one month because the Caesar of Washington gave orders to make the Palestinians starve by besieging them."
Speaking on Iraq, al-Zawahiri praised al-Zarqawi but did not mention the Jordanian-born Islamist's death in Iraq on Wednesday at the hands of US and Iraqi security forces.
Aljazeera said that the tape was made before the announcement of al-Zarqawi's death, because al-Zawahiri praised the al-Qaeda in Iraq leader's efforts to confront US-led forces in Iraq.
Al-Zawahiri criticised Sudan's
government for 'joining the US'
He sent greetings to the Shura Council of Mujahidin in Iraq and anti-US fighters, "who are confronting Crusaders and their apostate aids and the merchants of religion".
On developments in Sudan, al-Zawahiri concentrated on the situation in Darfur, criticising the visit by UN Security Council security experts to Sudan as being "to prepare to occupy and divide it".
"The spineless Sudanese government ... is joining the United States in dividing Sudan to stay in power," he said.
Al-Zawahiri accused Omar al-Bashir, Sudan's president, of inaction in the face of the "plot" to divide Sudan, "for the sake of keeping his position as a ruler".
He said: "I call upon every Muslim and everyone who has faith in Sudan, and every fervent Muslim in Darfur to confront the Zionist Crusader plot to occupy the lands of Islam."
Talking about the campaign by a group of Egyptian judges for full independence of the judiciary, al-Zawahiri, who is Egyptian, urged judges to apply Islamic law.
"Oh judges, you won't obtain independence unless your country is liberated first, and our home will not be liberated unless Islamic Sharia [law] is implemented," he said.
Addressing the judges, he said, "the regime won't give you your independence because to do so would be to kill itself".
But al-Zawahiri also blamed the judges: "I have to be frank with you. You are part of the problem. You agreed on the constitution and the secular laws imposed on the nation by arms and suppression and torture and rigged elections."