HARARE, Zimbabwe — Security officials arrested three senior officials of the Movement for Democratic Change, Zimbabwe’s main opposition political party, and a renowned human rights lawyer on Sunday, one day after a largely peaceful referendum on a draft constitution.

The lawyer, Beatrice Mtetwa, was arrested at the home of Thabani Mpofu, a top adviser to Morgan Tsvangirai, Zimbabwe’s prime minister and the leader of the M.D.C., whose house was raided by plainclothes police officers on Sunday morning, witnesses said.

The arrests follow months of harsh crackdowns on opposition politicians and civic groups in Zimbabwe ahead of a presidential election that is expected to be held this year.

“There is a very clear, broad campaign going on,” said Frances Lovemore of the Counseling Services Unit, an organization that provides medical and mental health services to victims of political violence. It was one of the first organizations to be singled out last year, and several employees were arrested in November.