The threats coincide on Sunday with the annual commemoration of the destruction of an ancient Jewish temple, considered one of the bleakest days in the Jewish calendar. A mass gathering of extremist Jews is scheduled in Jerusalem's Old City.
Hundreds of police officers and paramilitary troops have been deployed in and around the Old City to prevent a possible clash between Jewish extremists and Palestinian Muslims.
Thousands of Muslims already have arrived at the Haram al-Sharif, or Noble Sanctuary, compound to repulse any attempts to storm it. The compound shelters the Dome of the Rock and al-Aqsa Mosques.
The extremists are affiliated with several messianic Jewish groups, including Revava, which calls for the destruction of the al-Aqsa Mosque and the building of a Jewish temple on its site.
Israeli security have barred Muslims below the age of 45 from accessing the mosque's compound, Israeli police sources said on Sunday.
Messianic Jewish groups call
for the destruction of al-Aqsa
Palestinian Waqf officials in Jerusalem said they were taking Jewish threats very seriously.
"The threats have never ceased since 1967, hence we are always on high alert to thwart such attacks on Islamic holy places in Jerusalem," said Shaikh Muhammed Hussein, the top Muslim administrator in Jerusalem.
He told Aljazeera.net that thousands of Muslims from Jerusalem and Israeli were converging at the al-Aqsa Mosque esplanade to "protect it from any aggression".
"We can't rely on assurances from the Israeli government. The Israeli occupation authorities are not neutral in this regard. Hence, we have to be vigilant and not leave anything to chances."Draconian measures
Hussein criticised the Israeli police for preventing Palestinians from the West Bank from entering Jerusalem, calling the measure "draconian and starkly incompatible with Israeli claims about religious freedom".
Israeli security forces have been
deployed in Jerusalem's Old City
"I know of no other country that prevents the followers of a given religion from accessing their respective holy places."
Last year, the Israeli Interior Ministry allowed Jews, including extremist messianic elements, to visit the Haram al-Sharif, which Jews call Har Habayt or Temple Mount.
However, officials at the Supreme Muslim Council, which oversees Islamic holy sites in Jerusalem, have said ultra-Jewish nationalists were utilising these visits to gain a "foothold" at the sanctuary. Israel concerned
A Jerusalem police spokesman told Aljazeera.net that the police were viewing the "renewed showdown" more gravely than usual, citing the relevance of Israel's imminent pullout of the Gaza Strip.
"The threats have never ceased since 1967, hence we are always on high alert to thwart such attacks on Islamic holy places in Jerusalem"
Shaikh Muhammed Hussein
Muslim administrator, Jerusalem
He said the Israeli security apparatus was concerned that the opponents of the withdrawal might try to commit a "provocative act" in Jerusalem or elsewhere to stop or delay the withdrawal.
Earlier, the former chief of Israel's chief domestic intelligence agency, Avi Dichter, warned that Jewish terrorists might try to assassinate Israeli Prime Minister Ariel Sharon or attack mosques in Jerusalem.
Ten years ago, a Jewish extremist, Yigal Amir, assassinated former Israeli prime minister Yitzhak Rabin for signing the Oslo Accords with the late PLO leader Yasser Arafat.Sharon unpopular
In recent weeks, graffiti calling for the assassination of Sharon were seen on walls in Jerusalem and many Jewish settlements in the West Bank.
Some of these compared Sharon to Adolf Hitler, accusing him of "uprooting Jews from their homeland".
Sharon has argued that the withdrawal from Gaza was necessary to save Israel from what he called "the demographic threat".
Sharon is to address the Israeli public on Monday to explain and defend the withdrawal.