Officials had earlier said that Arthur Mutambara, who leads another faction of the MDC, and Lovemore Madhuku, of the pressure group National Constitutional Assembly, were also detained.
However, Mutasa said that she did not see any MDC members carrying weapons while on the way to the prayer vigil, adding that the only people she saw carrying arms were the police.
Earlier on Monday, human rights lawyers asked Zimbabwe's courts for urgent medical attention to be given to Morgan Tsvangirai, leader of the Movement for Democratic Change (MDC).
Haru Mutasa, the correspondent in Harare for Al Jazeera, which is the only international broadcaster with a permanent presence in Zimbabwe, spoke to Alec Muchadahama, a lawyer who had been unable to get direct access to Tsvangirai.
"He is swollen all over the body and he has collapsed three times," he said.
Another lawyer said that he had seen Tsvangirai's injuries, but police had prevented him and other lawyers from having full access to opposition and civic leaders arrested in the crackdown.
"He was in bad shape, he was swollen very badly. He was bandaged on the head. You couldn't distinguish between the head and the face and he could not see properly," Innocent Chagonda said after visiting Harare police station where Tsvangirai was being held.
"I managed to see him from about 10 metres inside the police holding-fence at Borrowdale Police Station. They were being paraded," he said.
One government minister told Al Jazeera that opposition supporters had got what they deserved.
"Tsvangirai will never have a good word to say about his country," Skhanyiso Ndlovu, the minister of information, said. "He is a black stooge, he goes around asking for sanctions on his own people."
"There is no future for them [the MDC]. People are fed up with opposition groups who pocket money from donors."
Tsvangirai and other opposition officials were arrested on Sunday after police blocked their motor convoy from driving to a stadium where a prayer vigil was due to be held.
Witnesses said police also clashed with opposition supporters around the venue in the Harare township of Highfield.
"There have been several skirmishes between the police and some youths, people throwing stones, and the police firing tear gas"
Zimbabwean journalist in Highfield
Police said one protester was killed when 200 "thugs" attacked 20 policemen.
A statement from the MDC said a party official was "shot and killed in cold blood" by police who were now "using live ammunition on innocent people".
Riot police moved in force early on Sunday to head off the prayer rally, which police had said would violate a ban on political protests imposed after opposition supporters clashed with police in Highfield last month.
The organiser of the event, opposition group Save Zimbabwe Coalition, had argued that the ban should not apply to a prayer vigil.
Witnesses said later in the day police had fired tear gas at youths who were throwing stones at their patrols, taunting them and defying orders not move around in large numbers.
Riot police mounted road blocks on major highways into the township and searched vehicles for arms and questioned motorists about where they were going.
Police on Saturday accused some elements in the MDC of hiring and arming "thugs" to attack officers.
"As far as we are concerned that is a political rally, and we are going to stop that meeting," Wayne Bvudzijena, a police spokesman told a news conference.
Bvudzijena said he had no immediate information on the arrests.
Officials have increased curbs on opposition movements after violence broke out last month when riot police broke up an MDC rally despite a court order directing that it should be allowed.
State media said officials feared the rally was intended to launch street protests against Mugabe's government.
Hebson Makuwise, an MDC representative in London, told Al Jazeera that it was "high time he [Mugabe] dissappeared from the political scene in Zimbabwe."
Mugabe is getting desperate, he is beating up the peaceful people of Zimbabwe," he said.
Mugabe, 83, and in power since independence in 1980, dismisses the MDC as a puppet of Zimbabwe's former colonial master, Britain.
Source: Al Jazeera and agencies