Masked men detained one of the last high-profile opposition figures still free in Belarus on Wednesday, his colleagues said, the latest in a series of detentions and expulsions of those leading mass protests.

Maxim Znak, who had worked as a lawyer for jailed presidential hopeful Viktor Babaryko, had been due to participate in a video call but did not show up, instead sending the word “masks” to the group, Babaryko’s press service said.