CAIRO, Egypt -- Police and plainclothes security men beat and arrested demonstrators calling for a boycott of Wednesday´s government-backed referendum on constitutional changes that would clear the way for Egypt´s first multicandidate presidential election.

Opponents say the referendum does not go far enough in advancing democracy, contending the rules being laid down ensure that President Hosni Mubarak will have no serious challengers and that his ruling National Democratic Party will keep its grip on power.

It was difficult to find people at the polling stations Wednesday who said they planned to vote "no," but it wasn´t clear whether this was in protest or disinterest in voting for a measure widely expected to pass.

"Of course I would say ´yes,´ because the president doesn´t sleep all night because he is serving us. He looks after our interests," said Saaban Mohammed Ahmed, a 42-year-old shopkeeper among about 15 people waiting for a downtown polling station to open.

Several opposition groups called a boycott of the vote and some planned referendum-day demonstrations despite heavy security.

Scattered anti-Mubarak demonstrations took place in defiance of warnings, some on the margins of pro-Mubarak street rallies, with scattered reports of violence. Many gatherings were broken up by force.

In one, more than a dozen members of the anti-Mubarak movement Kifaya, or "Enough," were beaten by pro-Mubarak gangs in Cairo. The protesters sought police protection but a high-ranking officer ordered lawmen to withdraw and allowed the attackers to set upon the demonstrators.

Elsewhere in the capital, 150 pro-Mubarak protesters attacked Kifaya members, belting them with wooden sticks use to hold Mubarak banners. Demonstrators scattered, with some taking refuge inside the press syndicate building.

One woman trying to leave the building was pounced upon by Mubarak loyalists who punched and pummeled her with batons and tore her clothes. As police looked on, the woman screamed, then vomited and fainted.

Another clash occurred when demonstrators placed Kifaya stickers onto placards emblazoned with Mubarak´s face and waved them in the air, chanting, "Leave, leave Mubarak!"

An Associated Press reporter on the scene said plainclothes state security investigators were beating, groping and verbally harassing demonstrators, particularly women.

About a dozen people, mostly women, were violently cornered and surrounded by nightstick-toting plainclothes police. Some began beating demonstrators. The AP reporter was grabbed and pulled by the hair.

Kifaya spokesman Abdel Halim Qandil said two group members were hurt. Police said 10 demonstrators were arrested.

"This is the first time this sort of beating and humiliation has taken place here in Cairo," Qandil said, but added it has been a problem in provincial areas.

In downtown Cairo, about 350 state-run TV workers rallied outside their office building, waving Egyptian flags and carrying banners urging people to vote.

Egyptian television showed video of Mubarak, his wife and his sons Alaa and Gamal, with the president dropping his vote in a ballot box.

Mubarak has led Egypt since soon after President Anwar Sadat was assassinated in 1981, and he has been reinstalled every six years in "yes" or "no," single-candidate referendums, which he is now trying to end. Mubarak hasn´t formally announced he will run again but is widely expected to do so.

Egypt´s opposition leaders are relatively unknown, with the exception of the popular Muslim Brotherhood, which favors the establishment of an Islamic state. The Brotherhood, the country´s oldest and largest Islamic movement, has urged its supporters to boycott the vote.

The amended article would replace references to presidential referendums with references to elections and stipulate some rules. Most controversially, it requires independent candidates to get 250 recommendations from elected members of parliament and local councils _ which all are dominated by Mubarak´s party _ before being allowed to enter the race.

The measure needs support from at least 51 percent of voters to pass. If it passes as expected, an election law would need to be crafted laying out specific rules and guidelines for the September election. ___Associated Press reporters Maggie Michael, Sarah El Deeb and Pakinam Amer contributed to this report. (Copyright 2005 Associated Press. 05/25/05)