WARSAW — Several popular Polish websites are planning to go dark for an hour Tuesday evening to protest the government's plan to sign an international copyright treaty.

Poland's support for the Anti-Counterfeiting Trade Agreement, or ACTA, has sparked days of Internet protests by groups who fear it could lead to online censorship.

The sites that are protesting are primarily ones that are popular with young people and that carry a mix of celebrity news, jokes, funny photographs and other entertaining material.

One site — www.wykop.pl — said that "under the banner of fighting piracy and concerns about intellectual property, ACTA will limit limit the rights of each of us."

ACTA shares some similarities with the hotly debated Stop Online Piracy Act in the U.S., which was shelved by lawmakers last week after Wikipedia and Google blacked out or partially obscured their websites for a day in protest.

In recent days, a group calling itself "Anonymous" attacked Polish government websites, leaving several paralyzed on Sunday and Monday. On Tuesday, most appeared to be working again, though the prime minister's site was unreachable. Still, Polish leaders are vowing to stick to plans to sign ACTA in Tokyo on Thursday.

ACTA has been negotiated by a number of industrialized countries that have been struggling for ways to fight counterfeiting and intellectual property theft — crimes that cause huge losses to the movie and music industries and many other sectors.

The far-reaching agreement would cover everything from counterfeit pharmaceuticals to fake designer handbags to online piracy. The U.S. government calls it "a groundbreaking initiative by key trading partners to strengthen the international legal framework for effectively combating global proliferation of commercial-scale counterfeiting and piracy."

The United States signed ACTA in October in Tokyo along with seven other countries: Australia, Canada, South Korea, Japan, New Zealand, Morocco and Singapore.

Now it awaits signing by a number of other parties involved in negotiating the agreement, including the European Union, Mexico and Switzerland, according to the website of the Office of the United States Trade Representative.

Critics of ACTA accuse the negotiating countries of hammering out the agreement in secret and failing to consult with the broader societies along the way.