Zimbabwe police have arrested one of the chief opponents to Robert Mugabe's government during a blockade to a protest prayer rally planned for Sunday.

Organisers had planned to address Zimbabwe's spiralling economic and political crisis at the rally organised by The Save Zimbabwe Campaign, a coalition of church, rights and opposition groups campaigning for political change in the country.

It was quickly thwarted, however, by truckloads of armed police who prevented local residents from getting to the stadium in the Harare township of Highfield where the rally was due to take place.

Riot squads arrested main opposition leader Morgan Tsvangirai, head of the Movement for Democratic Change (MDC) party, along with dozens of other MDC officials and activists, while one MDC activist was shot dead. Police said he had ignored warning shots after leading a gang of protestors in hurling rocks at the police.

"They were ordered to disperse but began to advance menacingly at the officers," said Wayne Bvudzijena, national police spokesman, in an AFP report.

"Warning shots were fired and the group still advanced. The police shot one male adult who appeared to be the leader of the group in the chest. He died on the spot and the group dispersed."

Organisers of the rally had vowed to go ahead with the rally despite the imposition of a ban on political rallies last month, arguing that prayer vigils should not be included in the ban.

According to The Save Zimbabwe Campaign, shops, bars and churches were forced by the riot police to shut for the day.

Just last week, Christian humanitarian agencies Tearfund and Christian Aid spoke out against President Mugabe's ruling ZANU PF part for putting pressure on church groups carrying out human rights work. The crackdown includes the recent arrest of eight church leaders and the closure of the office of a church-based human rights organisation - funded by Christian Aid - in Harare.

"This harassment is unacceptable," said Christian Aid's Africa policy manager, Babatunde Olugboji.

"State services have all but collapsed in Zimbabwe and the poor have limited access to healthcare, education, clean water, food and other essentials. Aid agencies are playing a major role in keeping people off the bread line," said Mr Olugboji.