Two more people were taken into police custody on Thursday, as part of a crackdown on the communications office of Prime Minister Morgan Tsvangirai.

Spiwe Vera and Elizabeth Banda, who work as caretakers in the Avondale based office, were picked up by police on Thursday morning and taken to Harare Central Police Station. They were detained and questioned throughout the day.

According to lawyer Dr. Tarisai Mutangi, the two were released without charge late on Thursday afternoon.

It is understood they were interrogated as part of investigations launched by the police, which saw the arrest of four others linked to the communications office on Sunday. Thabani Mpofu, Felix Matsinde, Mehluli Tshuma and former Harare City councillor Warship Dumba, remain in police detention after being remanded in custody until April 3rd.

Mpofu, Matsinde and Dumba are all members of staff in the research division of the Prime Minister's office, while Tshuma is believed to have been assisting the research team. Police also arrested another member of staff in the communications office, Anna Muzvidziwa, but she was released on Sunday night.

Mpofu's lawyer, Beatrice Mtetwa, was also arrested after asking the police to produce a search warrant. She too remains in police detention.

Mpofu, Matsinde, Tshuma and Dumba have been formally charged for allegedly impersonating police, possession of articles for criminal use and breaching the Official Secrets Act.

There are no further details about what prompted the police crackdown, but there are suggestions Mpofu and his three co-accused were compiling a dossier on large scale corruption by some senior government officials.

A statement from the Prime Minister's office on Thursday said this "attack" on his office is "an affront to democracy and to the rule of law."

"It is an attack not only on the members of staff but also on the institution of the Office of the Prime Minister," the statement read.

Numerous attempts to get comment from the Prime Minister's spokesperson, Luke Tamborinyoka, were in vain as his phone went unanswered on Thursday.