MINSK, Belarus (AP) — Police in Belarus said Wednesday that officers detained more than 250 people the previous day, after mass protests against barring two candidates from the upcoming presidential election erupted in the country.

Thousands of people took to the streets of Minsk and other cities Tuesday, protesting against the exclusion of two main rivals of authoritarian President Alexander Lukashenko from taking part in the Aug. 9 election.

The country’s central election commission allowed five candidates on the ballot, denying spots to Valery Tsepkalo, founder of a successful high-technology park, and former banker Viktor Babariko. The decision eliminated any serious competition for Lukashenko, who is seeking a sixth term after a quarter-century in power.

Protesters gathered in the center of Minsk, with police blocking several streets and closing off the capital's central subway station to discourage the crowds. Footage of the rally showed people marching down the city streets and clapping — a popular protest gesture in Belarus — and police officers clashing with some of the protesters while trying to detain them.

Amnesty International on Wednesday condemned mass detentions as provoking violence and violating protesters' rights.

“The police sought to disperse peaceful gatherings, with excessive and unnecessary use of force and in many cases deploying police officers in plainclothes. This provoked violent responses from some protesters who tried to prevent others being arrested and beaten," Aisha Jung, Amnesty International's Belarus Senior Campaigner, said in a statement.

“However, according to eyewitnesses and widely available video footage, the gatherings remained largely peaceful, and many of those arrested were peaceful protesters," Jung said.

Interior Ministry spokeswoman Olga Chemodanova insisted Wednesday that police demonstrated “self-restraint and high professionalism” despite “the aggression of certain individuals.”

According to Vesna, a human rights advocacy group in Belarus, more than 900 people have been detained during protests that accompanied this year’s presidential campaign.

The 65-year-old Lukashenko, who has run the nation of 9.5 million people with an iron fist and relentlessly cracks down on political opposition and independent media, accused the protesters of plotting a revolution and promised to protect the country from it.

“We will be defending the country with any lawful means. We will not surrender our country to anyone,” the president said Wednesday.

The Office for Democratic Institutions and Human Rights of the Organization for Security and Cooperation in Europe said in a statement Wednesday that it won't be deploying an election observation mission to Belarus due to a “lack of invitation” from the country's government.