CAIRO — Egypt has rounded up at least six activists in the last two days in a wave of arrests coinciding with the anniversary of the 2011 uprising, a rights lawyer said Wednesday.

Authorities have waged a sweeping crackdown on dissent in recent years, reversing freedoms won in the popular uprising that toppled longtime autocrat Hosni Mubarak. Security is especially tight around the anniversary of the Jan. 25 uprising.

Negad Borai, the lawyer, said that among those arrested was Yehia Hussein Abdel Hady, the former spokesman of the Civil Democratic Movement. The coalition of secular and left-leaning political parties had called for a boycott of Egypt’s presidential election last year.

The other five activists were arrested Monday after they attended a ceremony commemorating the uprising, Borai said. The five were members of the Karama, or Dignity, party founded by opposition leader Hamdeen Sabahi, the only candidate to run against President Abdel-Fattah el-Sissi in the 2014 presidential election.

The whereabouts of the six activists are still unknown, Borai said. It was not clear if they were among 54 people who authorities said Tuesday were detained for plotting to foment chaos.

associated press