Authorities in Belarus detained a lawyer representing a top opposition activist who was jailed this month amid mass protests against the country's authoritarian president, who won a sixth term in a disputed election.

The lawyer, Lyudmila Kazak, went missing Thursday, with police confirming later in the day that she had been detained. According to Kazak’s lawyers, she faces administrative charges of participating in an unauthorized rally and resisting a police officer.

Kazak was defending Maria Kolesnikova, a key member of a council Belarus' political opposition set up to push for a new presidential election. Kolesnikova is facing charges of undermining state security that could bring a five-year prison term, if she is convicted.

Kazak relayed several messages Kolsenikova sent from jail, encouraging protesters to continue anti-government rallies that have rocked Belarus for nearly seven weeks.

“Freedom is worth fighting for. Do not be afraid to be free,” one such message said. “I do not regret anything and would do the same again.”

Kolsenikova has said Belarusian security forces drove her to the border with Ukraine to try to make her leave the country, but that she tore up her passport. She alleged officers threatened to kill her.

Her lawyer's detention followed the arrest of Yegor Martinovich, chief editor of popular independent news outlet Nasha Niva. Martinovich is accused of slander against a government official, and faces up to three years in prison.

Hundreds of thousands of Belarusians have been protesting daily since the Aug. 9 presidential election. Official results extended the 26-year tenure of President Alexander Lukashenko, giving him 80% of the vote. Lukashenko's strongest opponent, Sviatlana Tsikhanouskaya, got 10% support.

Both opposition members and some poll workers say the vote was rigged, and the United States and the European Union condemned the election as neither free nor fair. Many European countries refused to recognize Lukashenko as the legitimate leader after his unexpected inauguration earlier this week.

Anti-Lukashenko protests have rocked the country daily since the election, with the largest rallies in Minsk attracting up to 200,000 people. In the first days of protests, police used tear gas, truncheons and rubber bullets to disperse crowds. Several protesters died, many were injured and nearly 7,000 were detained.

The response to street demonstrators intensified again this week, with police detaining hundreds and injuring many. Despite the crackdown, protests continued in Minsk on Friday, with groups of people in different parts of the capital forming human chains of solidarity and singing songs.

Daria Litvinova in Moscow contributed to this report.