MINSK, Belarus —  Security agents detained at least 16 journalists in Belarus and searched their homes and offices for materials that allegedly libel authoritarian President Alexander Lukashenko, activists said Thursday.

A Polish-funded radio broadcaster said 20 of its Belarusian employees had been detained. The Belarusian Journalists' Association counted at least 16 journalists summoned for questioning by the KGB, the country's top security agency, or had their apartments searched.

The State Department put the number at 30 journalists detained in 12 cities.

The nationwide raids follow a protest on Tuesday by opposition and other activists in the capital, Minsk, in defiance of a government ban on marking a historical holiday. Dozens were arrested.

KGB agents raided the offices of Radio Racja and European Radio in Minsk, and private apartments throughout the country, association chief Zhanna Litvina said. The two radio stations receive funding from the European Union. Correspondents affiliated with U.S.-funded Radio Liberty were also detained.

"This reminds us more of Stalin's time, not Europe in the 21st century," Racja reporter Yulia Kotskaya said.

Litvina said the searches appeared to have been ordered in retaliation for the coverage of Tuesday's protest, when thousands marked the holiday that the opposition has traditionally called Freedom Day.

In Poland, Agnieszka Romaszewska, who heads the government-funded Belsat TV company, which broadcasts Belarusian-language programs, said about 20 journalists, mainly with Belsat, were detained and broadcasting equipment was confiscated.

KGB officials refused to comment on the searches. Deputy Prosecutor General Alexei Stuk said investigators were looking for materials related to animated cartoons that were circulating on the Internet and that were broadcast on Belsat.

"The investigation is looking into whether journalists are cooperating with the creators of the cartoons that insulted Lukashenko," Stuk said.

Libeling the president in Belarus is punishable by up to four years in jail.

Lukashenko has ruled the ex-Soviet republic since 1994.

The country's Foreign Ministry said the searches were conducted only for journalists deemed to be working illegally in Belarus. Radio Racja, European Radio and Belsat had all been denied government accreditation.

Polish President Lech Kaczynski on Thursday expressed "deepest possible anxiety" about the situation, adding, "The events in Belarus are not a return to previous situation, but rather it's worsening."

European Union officials criticized the arrests. State Department spokesman Sean McCormack called for the journalists' release and said Lukashenko's regime "has again shown itself as a brutal, authoritarian dictatorship that blatantly ignores human rights and fundamental freedoms."

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