"Members of the public are no longer allowed to practice urban agriculture as this has devastating effects on the environment,'' the radio said.
The opposition Movement for Democratic Change (MDC) said the ban would have a devastating effect on urban households.
"Many families in urban areas have survived on what they grow,'' said the party's shadow agriculture minister, Renson Gasela.
City dwellers, many of them opposition supporters, have already been hard-hit by a police crackdown launched a month ago against illegal market traders and street vendors.
Soaring food prices and worsening shortages had forced many city dwellers to grow their own small crops of cereals like maize, often on open pieces of land or on river banks.
Meanwhile the U.S.-funded monitoring body Famine Early Warning Systems Network (FEWSNET) warned in its latest report that food security in urban areas was deteriorating.
It said that while in northern rural areas maize and other cereals are "still generally available'', in the southern parts of the country supplies have been severely affected by the police clean-up campaign.
"If (official) supplies do not increase to make up for the reduced informal trade, the situation will be even worse next month in the southern districts,'' it added.
Meanwhile the state-owned Herald newspaper reported on Tuesday the arrest of nearly 500 people, including 161 foreigners, in central Harare as the "Operation Restore Order'' campaign continues.
A police spokesman said 335 "prostitutes'' and 161 immigrants from Rwanda, the Democratic Republic of Congo (DRC), Mozambique, Malawi, Zambia, Algeria, Ghana and Liberia had been detained.
Some of the immigrants were being held at Harare Remand Prison "awaiting deportation'' while others have already been repatriated.
"We are a friendly country and not enemies to the various countries that had their citizens affected,'' the police spokesman said.
"What we are saying is that they should use the proper channels when visiting Zimbabwe,'' the police spokesman said.
President Robert Mugabe says the blitz on Zimbabwe's cities, in which up to 30,000 people have so far been arrested and hundreds of shacks and shanty towns destroyed, is an attempt to create a "salubrious'' new environment.
The MDC calls the campaign an attack on its supporters, most of whom reside in urban areas. dpa rt ch
- Deutsche Presse Agentur
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