Two foreign journalists were detained and rooms used by Zimbabwe's opposition Movement for Democratic Change were reportedly raided on Thursday.
The developments were "an ominous sign that President Robert Mugabe might turn to intimidation and violence," reported Angus Shaw, the experienced Harare correspondent of The Associated Press.
One of the journalists arrested was Barry Bearak, a New York Times correspondent based in Johannesburg who was on assignment in Harare. Police told Agence France-Presse that he had been taken into custody for reporting without accreditation. The identity of the other journalist was not known.
The MDC's secretary-general, Tendai Biti, told AP that hotel rooms used as offices were ransacked by people he believed were police or intelligence agents.
"Mugabe has started a crackdown," he told AP. "It is quite clear he has unleashed a war."
At the same time the Zimbabwe Electoral Commission released the first results of the election for Zimbabwe's senate - the ruling Zanu PF and the MDC had won five seats each, it said.