Belarusian authorities have arrested some 26 people following a wave of major protests against authoritarian President Alexander Lukashenko, state television said Thursday, citing security services.
State channel STV cited the powerful KGB security agency as saying that the arrests were part of a probe into the preparation of mass unrest.
Earlier Vyasna, an NGO that defends the rights of political prisoners, said 17 people were detained in this week's wave of arrests in the ex-Soviet country bordering Russia and the European Union.
The EU called for their immediate release and said it was in contact with Minsk authorities, urging restraint.
Among those held was prominent activist Zmitser Dashkevich, who was jailed for two years in 2011 after attending a mass rally opposing Lukashenko's re-election.
In recent weeks, thousands have protested against Lukashenko's rule and a controversial new tax on "spongers" -- those who work less than six months a year -- as the country suffers an economic slump.
The biggest round of opposition protests yet is planned for Saturday.
Television reports claimed the detainees were planning to stage "provocations" during Saturday's rally and that a weapon cache had been uncovered.
The latest arrests began overnight Tuesday to Wednesday after Lukashenko said police had detained several dozen people who underwent weapons training at camps in Belarus and elsewhere.
Lukashenko said they had been "preparing an armed provocation."
The detainees are being held in KGB-controlled prison and have not been allowed to meet with lawyers, Vyasna said.
It said some are being held on suspicion of training people to participate in mass protests involving violence or armed resistance.
On Wednesday, Vyasna said at least six people had been detained but upped the number on Thursday to 17.
- Opposition figures, journalists -
Belarusian state-controlled television on Wednesday showed an activist detained with a replica hand grenade and a firearm as well as the Ukrainian Insurgent Army (UPA) flag.
The UPA was a group of Ukrainian nationalists who fought against Soviet troops in World War II alongside Nazi forces.
State ONT television said the activist was a member of radical nationalist group Bely Legion, or White Legion, which is generally believed to have disbanded in the late 1990s.
Another of the detainees was identified by Vyasna as bookseller Miroslav Lozovsky, who had previously been linked to White Legion.
Dozens of protesters, including journalists and opposition leaders, were hauled in after the recent protests, receiving fines or up to 15 days in police cells.
The European Union last year lifted most of its economic sanctions against Belarus after Lukashenko, who has led the country since 1994, took steps to appease the West, including by releasing political prisoners.
"Recently detained peaceful protesters must be immediately released," said a spokeswoman for the EU's foreign affairs office on Thursday.
"We are in touch with Belarusian authorities in order to pass necessary messages calling for restraint."