Millions of Moroccans are heading to the polls to vote on King Mohammed's controversial constitutional reforms he unveiled in response to his country's pro-democracy uprising.

Officials estimated that turnout by midday Friday was about 25 percent of the some 13 million eligible voters. Preliminary results are expected after polls close Friday evening.

King Mohammed announced his proposed reforms last month. The referendum would limit his power while strengthening parliament and the prime minister's office.

But the country's youth-based pro-democracy movement has criticized the proposed changes for not meeting what they called “demands for a true separation of powers.”

Critics say the new constitution still keeps King Mohammed firmly in power by allowing him to choose the prime minister from the party that won elections and continue to oversee the country's religious matters, security apparatus and judiciary.

It also allows him to dissolve parliament, though not unilaterally.

In February, pro-democracy demonstrations swept across Morocco like much of North Africa and the Middle East. However, the effect of the so-called “Arab Spring” movement has been somewhat muted in Morocco compared to the protests that toppled rulers in Tunisia and Egypt.

The 47-year-old King Mohammed took over the Arab world's longest-serving dynasty in 1999. He currently holds virtually all power in the Muslim north African country and is its top religious authority.