RIYADH (AFP) - Leaders of the six Gulf monarchies began an emergency meeting in Riyadh Thursday on the Gaza crisis amid differences over how to respond to the Israeli onslaught. The extraordinary summit was hastily organised following a call by Saudi King Abdullah, while neighbouring Qatar pushed to hold an emergency Arab summit on Friday to address the same issue, despite an apparent lack of quorum. Leaders of Bahrain, Kuwait, Qatar, and the United Arab Emirates, in addition to King Abdullah, are taking part in the Riyadh summit. Oman is represented by Vice-Prime Minister Fahd bin Said. The Saudi monarch called the Thursday summit due to escalating tensions "resulting from the Israeli aggression against the Palestinian people," according to the official SPA news agency. Saudi Arabia has accused Israel of "racist extermination" and sweeping human rights abuses. Qatar meanwhile continued to prepare for its proposed summit, although Arab League chief Amr Mussa said in Kuwait on Wednesday that a quorum of 15 countries to hold the meeting in Doha had not been achieved, as only 13 of the 22 member states had agreed to attend. Sudanese President Omar al-Beshir was the first leader to arrive, according to Qatar's official news agency QNA, while Mauritanian state press agency AMI reported that General Ould Abdel Aziz, leader of the junta that seized power last August, had set off from Nouakchott for Qatar. Members of a Syrian delegation which arrived Thursday in Doha said that President Bashar al-Assad was to arrive within hours, while Algerian diplomats said President Abdelaziz Bouteflika is expected to come. In Lebanon, a government official told AFP that President Michel Sleiman was heading to Qatar but would attend the summit only if the 15-state quorum is achieved. Meanwhile, Morocco's King Mohammed VI hit out angrily Friday at the Arab world's failure to respond in a united way over Gaza and ruled out his attendance at two summits earmarked for discussing the crisis. The King issued a statement condemning "a pathetic Arab situation that had achieved a state of disrepair without precedent in the history of common Arab action." King Muhammad said he would attend neither an emergency Arab League summit that Qatar is trying to organise for Friday in Doha nor an economic summit in Kuwait next week.