Israeli Prime Minister Ariel Sharon, suffering from a significant stroke on late Wednesday, underwent a lengthy surgery in a Jerusalem hospital earlier on Thursday and is now in critical condition.

Sharon's grave illness has drawn mixed reactions from the Palestinians as some officials voiced concerns over the possible repercussions in the Israeli political landscape and the future prospects of the peace process while Islamic militant groups expressed joy.

CONCERNS OVER SHARON'S CONDITION: ABBAS

Palestinian President Mahmoud Abbas expressed concerns over the health condition of Sharon, Abbas' aide Nabil Abu Rudeineh told reporters.

Abu Rudeineh said that Abbas voiced his concerns about Sharon's health in a phone call to senior Israeli officials.

Abbas and Sharon announced a de facto truce deal in a landmark summit on Feb. 8, which led to a 10-month-long relative calm period.

SHARON'S ABSENCE TO LEAVE POLITICAL VACUUM: QUREI

Palestinian Prime Minister Ahmed Qurei said that the absence of Sharon will leave a political vacuum in Israel.

Qurei told reporters in the West Bank city of Ramallah that he was closely following reports on Sharon's condition.

The Palestinian prime minister wished Sharon a speedy recovery, adding that the Palestinians were looking toward an Israeli leadership that supports peace and is able to negotiate with the Palestinians.

Qurei also said that the Israelis would miss Sharon as a leader and a decision maker.

NO DRAMATIC CHANGE IN ISRAELI POLICIES NOW: SHAATH

Palestinian Deputy Prime Minister Nabil Shaath asserted that there would not be any dramatic change in Israeli policies toward the Palestinians till the March 28 Israeli general elections even if Sharon could not run the government.

He also said, "I don't think that there will be another leader among the Israelis like Sharon, although his deputy Ehud Olmert is seen as sharing the same ideas as his."

NEW PEACE-PRONE ISRAELI LEADERSHIP: EREKAT

Palestinian chief negotiator Saeb Erekat told reporters that first of all he wishes quick recovery of Sharon, adding that the Palestinian leadership is keeping a close watch on Sharon's health condition with great concern.

"If Sharon either quits political life or passes away, we call on the Israeli people to choose a new Israeli leadership, a new government that believes in peace and negotiations, but not in military operations," said Erekat.

BETTER MIDEAST WITHOUT SHARON: HAMAS

Musheer al-Masri, spokesman of the Islamic Resistance Movement (Hamas) in the Gaza Strip, said that the Middle East region would be a better place without Sharon.

Criticizing Sharon as "aggressive" toward the Palestinian people, al-Masri also urged the Palestinian leadership not to be influenced by changes in the Israeli political life due to Sharon's grave illness.

However, senior Hamas leader Osama Hamdan indicated that the absence of Sharon would have a negative impact on the Mideast peace process.

"The absence of Sharon would have an impact on the situation in Israel and the peace process would be negatively affected," said Hamdan, calling upon the Palestinians to get prepared for changes due to Sharon's failing health.

Hamas, a popular Islamic militant group, is sworn to Israel's destruct. Spearheading five years of violent resistance against the Israeli occupation, the group is slated to run in the coming Palestinian legislative elections due on Jan. 25 and is widely expected to do well in its first parliamentary bid.

RESISTANCE TO CONTINUE WITH OR WITHOUT SHARON

Anwar Abu Taha, a senior leader of the Islamic Jihad(Holy War), said that Jihad was determined to continue armed struggle with or without Sharon until the Palestinian people get their legitimate rights.

He also termed Sharon as "one of the tyrants who has committed scores of bloody massacres against the Palestinian people."

Hours before Sharon was taken to hospital on Wednesday night, Saraya al-Quds, armed wing of the Islamic Jihad, fired about 12 homemade rockets at Ashkelon in southern Israel, wounding two Israelis.

The Israeli Daily of Maariv reported that Sharon was holding a meeting with senior security and army officials when the rockets were fired.

Learning about the rocket barrage, Sharon hit the table and screamed to stop such attacks by all means immediately, according to the report.

The Islamic Jihad also vows to destroy Israel and is behind some of the most deadly attack on Israeli targets.