By Souhail Karam and Mark John

RABAT (Reuters) - Morocco's "Arab Spring" protesters said they were undeterred despite a landslide victory for King Mohammed in a referendum on constitutional changes they say do nothing to ease his autocratic grip on power.
Preliminary results of Friday's poll showed 98.5 percent of voters approved the text on turnout officials estimated at 73 percent. Opposition said the turnout figure looked inflated and alleged irregularities in voting procedures.
The charter explicitly grants executive powers to the government but retains the king at the helm of the cabinet, army, religious authorities and the judiciary.

The result followed a state media campaign in favor of the "yes" vote that appealed to a widespread sense of loyalty to the king, who is head of the Arab world's longest-serving dynasty and a staunch Western ally.
The result will also be scrutinized by Gulf monarchies who have so far dodged reform calls. Western partners of Morocco urged the king to enact reforms swiftly and to listen to the demands of representatives of citizen movements.

"We shall continue to be the only real opposition in this country, the opposition in the street," Najib Chawki, one of the coordinators of the leaderless "February 20" street movement, which wants a parliamentary monarchy under which the powers of the king and political elite are checked by the legislature.
"Tomorrow we will see how people react," he said of nationwide rallies the group has called for Sunday. Protests staged last Sunday drew tens of thousands to the streets of the capital Rabat, economic hub Casablanca and the port Tangiers.

Mohammed, 47, has had some success in repairing the legacy of human right abuses, high illiteracy and poverty he inherited after his late father's 38-year rule ended in 1999. Yet critics say there remains a wide disparity between rich and poor, and complain of failings over human rights and the rule of law.
Ali Bouabid, of the executive committee of the main Socialist Union of Popular Forces (USFP) party, queried voting procedures at his local polling station on his Facebook page.
"I handed in my voter's card and asked if they should verify my identity. I was told 'we don't do this'," he wrote.
Others questioned why only 13 million voters were registered from a total of nearly 20 million Moroccans of voting age.

"END OF THE BEGINNING"

The street movement has failed to attract the mass support of popular uprisings that toppled the leaders of Tunisia and Egypt, and the result raises questions over its future path.
In Bahrain, which began talks on Saturday between opposition and pro-government groups after protests earlier this year, the leading Shi'ite opposition group Wafeq gave the new constitution a cautious thumbs-up and said it could serve as a model.

"Even though the king will preserve presidential powers ... such as the sole privilege of appointing the security apparatus, the progress which this new constitution has brought is an important development in Morocco's path toward democracy," Wafeq said.
France, which maintains close links with the North African state which was once its protectorate, welcomed a "clear and historic decision" that contrasted to what it called the repression encountered by Syrian and Yemeni street movements.

In a statement, the European Union hailed steps to boost parliament's role and the independence of the judiciary and called on them to be implemented quickly and effectively.
"This is the end of the beginning. The referendum is just a step," said a Western diplomat who declined to be named.
"We now have to see how sincere the king is about reform ... They know that a crackdown will not go down well with the West."
Lise Storm, senior lecturer in Middle East studies at the University of Essex, said it appeared to be "game over" on any prospects of a genuine parliamentary monarchy for now.

"The international community should increase its pressure on Morocco to introduce significant reform, not just perform cosmetic surgery. Now is really the time, and the opportunity seems to have been wasted," she said.
Aboubakr Jamai, editor of the French-language version of independent news portal Lakome.com, said the king's ability to ensure ordinary Moroccans benefited from the economic growth seen at five percent next year could be critical.

"The monarchy remains under Arab Spring pressure to behave itself politically and economically," he said.
"If the king enjoys popularity among ordinary Moroccans it's because they are not aware how much of their social problems is the result of bad governance from the palace."

(Additional reporting by John Irish in Paris; Pete Harrison in Brussels; Isabel Coles in Bahrain; Writing by Mark John; Editing by Sonya Hepinstall)