Alyaksey Frantskevich, the leader of the Free Belarus Foundation who currently resides abroad, said on December 28 that police searched his home in Belarus.
According to Frantskevich, his neighbors were ordered to be present during the search as witnesses and forced to sign papers banning them from revealing details of the search.
Frantskevich's foundation is registered in Ukraine and is involved in assisting the Ukrainian armed forces fighting Russia's invasion.
The Crisis In Belarus
Read our coverage as Belarusian strongman Alyaksandr Lukashenka continues his brutal crackdown on NGOs, activists, and independent media following the August 2020 presidential election.
The Free Belarus Foundation also defends the rights of Belarusian citizens in Ukraine.
In a separate case, police in the Belarusian city of Homel detained a family of four on high treason charges, the Vyasna human rights center said on December 28.
According to Vyasna, construction worker Vasil Prokharau; his wife, Larysa, a nurse; and their son Paval, who is also a construction worker, may face up to 15 years in prison if found guilty.
It was not immediately known what the charge stemmed from.
Meanwhile, the Mediazona website said on December 28 that a Minsk resident was arrested on charges of spreading false information about fighters from Russia's Wagner mercenary group who stayed for a short period of time earlier this year near the eastern Belarusian town of Asipovichy following a short-lived mutiny against Russian authorities that was led by the group's late leader Yevgeny Prigozhin.
Authoritarian Belarusian ruler Alyaksandr Lukashenka, a close ally of Russian President Vladimir Putin, was involved in talks to end the mutiny, agreeing to host the Wagner troops and Prigozhin in Belarus.
Prigozhin was killed in a plane crash in August.
Many activists, journalists, and representatives of democratic institutions have been jailed in Belarus since an August 2020 presidential election that officially named Lukashenka the winner but which opposition politicians, ordinary Belarusians, and Western governments said was rigged.
The United States, the European Union, and several other countries have refused to acknowledge Lukashenka as the winner of the vote and imposed several rounds of sanctions on him and his regime, citing election fraud and the crackdown against protesters.