HARARE: Zimbabwe police detained three senior aides to Prime Minister Morgan Tsvangirai Sunday in the wake of a key referendum, the premier's office said.

They "were arrested in Harare this morning," a source in Tsvangirai's office told AFP, adding that the charges were not specified.

The three were detained by plain clothes police officers at their homes.

They were named as Thabani Mpofu, Anna Muzvidziwa and Felix Matsinde.

It is just the latest incident to mar Zimbabwe's constitutional referendum, which took place on Saturday.

The vote is expected to handily approve new laws to curb President Robert Mugabe's powers, while permitting him to remain in office for another decade.

Both Mugabe and his rivals back the text, but a decade of unrest and upcoming elections have hung heavy over the poll.

A group of MDC supporters were beaten on Friday and a party leader was seized by plainclothes police on referendum day.

Zimbabwe Lawyers for Human Rights said police who detained the latest group had been looking for a radio, but seized at least one document.

Zimbabwean police have launched a series of raids to seize two-way radios, a policy that rights groups say is a fig-leaf for intelligence gathering and intimidation.

The lawyers' spokesman Kumbirai Mafunda said he had also received word that a lawyer named Beatrice Mtetwa was seen being bundled into a police truck.