The authorities had earlier warned that anti-government rallies organised by the opposition leader, Michael Sata, posed a serious threat.

His supporters have been challenging the results of September's presidential election, which was officially won by incumbent President, Levy Mwanawasa.

On Thursday, a court dropped charges against Sata of making a false declaration of his assets.

Even after his election defeat, Sata has continued to draw large crowds at his rallies - and he has repeatedly accused the president of, as he puts it, selling Zambia to Chinese and Indian companies.

Sata's Patriotic Front party had said it would challenge the rally ban in court.

Last week, the president said the opposition leader, whose nickname is King Cobra, was on the verge of treason.