Grand Mufti Shaikh Taysir al-Tamimi told Aljazeera on Monday that the Revava settler movement had made it clear they intended to enter the site - by force if necessary - and that they should be stopped.
Israeli occupation forces have closed all gates of Jerusalem city, preventing Palestinians from reaching the shrine, Aljazeera reported.
Al-Tamimi said: "Israeli occupation forces should prevent settlers who have threatened to attack al-Aqsa mosque from approaching.
"But instead they are preventing Palestinians from coming to pray or allowing them to face these Jewish extremist groups ... who plan to destroy or occupy al-Aqsa this year in order to establish the so-called Temple."
OIC help sought
Al-Tamimi added that the Islamic Conference Organisation (OIC) was not doing enough to defend the site.
Palestinians shout anti-Israeli
slogans in the Old City on Monday
"The OIC unites all Muslim countries and has the ability to end this threat," he said. "This organisation was particularly established for this purpose ... the whole nation should carry out their responsibilities towards al-Aqsa."
On the ground, Israeli authorities said Palestinian protesters threw stones at Israeli police guarding a disputed holy site, slightly wounding seven officers, including Jerusalem's police chief.
Police spokesman Shmuel Ben-Ruby said the clash broke out after police barred several hundred Palestinian youths from reaching the site, which houses the Al Aqsa Mosque compound. The youths threw rocks at the officers, and Chief Ilan Franco received several stitches for a wound to his leg.
Ben-Ruby said police used stun grenades to disperse the crowd. He said there were no reports of injured protesters.
But Revava spokesman David Ha'ivri told Aljazeera.net that he expected Israeli police to allow group members to enter the site "and keep Palestinian terrorists from obstructing us".
"Once we get to the site we intend to pray. Jews have the right to pray on the land where the Temple was built."
However, last month only a few Revava members turned up for the demonstration and all were turned away by Israeli police.
Jewish settlers pray in front of
al-Aqsa mosque in April
Additionally, Aljazeera's correspondent in the city of Jerusalem - known to Arabs as al-Quds - said Israeli police were not expecting any form of demonstration, although they were only allowing Palestinians with Israeli identity cards over the age of 50 to enter the site.
However, three people were lightly injured in scuffles with Israeli police near the al-Aqsa museum.
Extremist Jews held
Meanwhile, Israeli authorities have put an extremist Jewish colonist under detention for five months without charge or trial to head off violence aimed at stopping Israel's Gaza Strip pullout
However, Jerusalem police spokesman Shmulek Ben Robby told Aljazeera.net there was no link between the arrest of the settler extremist, Neria Ofen, and possible plans to attack holy places in the old town of Jerusalem.
"You know, the whole thing is a rumour, we told the Islamic Wakf authorities that we will not allow the extremists to enter the mosques."
He also criticised Muslim leaders in Jerusalem and Israel proper for "responding disproportionately" and said it was "not right to bring thousands of people whenever there is a rumour of this kind".
But with Jewish extremists planning to resist the summer pullout, the army and politicians have discussed using the detentions to contain expected violence.
Khalid Amayreh contributed to this article