Correctional Services said that “matters are under control” at Johannesburg’s Sun City Prison on Wed.
Zimbabwe police ordered organisers of a prayer meeting to withdraw opposition leaders and "political speakers" from the programme on Saturday and let the meeting go ahead without them speaking.
As the meeting dispersed, there were no reports of arrests or incidents of unrest.
The organisers, the Save Zimbabwe Campaign, an alliance of Christian and pro-democracy groups, said key opposition figures showed "solidarity" by attending the vigil without addressing the congregation in Bulawayo.
Also present were regional clerics and church officials from neighbours Malawi, Zambia and South Africa.
Police kept their distance and did not intervene when youths chanted political slogans. Three water cannons were deployed nearby.
Bulawayo's Roman Catholic Archbishop Pius Ncube, an outspoken critic of the government who has vowed to lead illegal street demonstrations to protest state perpetrated violence and Zimbabwe's economic meltdown, spoke to the gathering of about 400 worshippers. - Sapa