MINSK, Belarus (AP) — Riot police in the Belarusian capital have raided the office of a human-rights group hours ahead of an attempt by opposition activists to mount a large protest march.

Authorities banned the demonstration planned for Saturday afternoon and dozens of police detention trucks were deployed in the center of Minsk.

The authoritarian former Soviet republic has seen an unusually persistent wave of protests over the past two months against President Alexander Lukashenko, who has ruled since 1994. After tolerating the initial protests, authorities cracked down. Lukashenko this week alleged that a "fifth column" of foreign-supported agitators was trying to bring him down.

About midday Saturday, police raided the office of the Vesna human rights group. About 30 people were detained, said Oleg Gulak of the Belarusian Helsinki Committee, another rights organization.