The wife of Zimbabwe's President Robert Mugabe complained on Wednesday that the cash-strapped country's economic woes were damaging her dairy business.

"I manufacture yoghurt but no one buys it," Grace Mugabe told supporters at a rally in the capital Harare. "You can't even find a person who can buy a packet of milk."

Mugabe's critics have branded the first lady "Gucci Grace" for her lavish lifestyle, designer clothes and shopping sprees abroad.

Grace Mugabe, who is 41 years younger than her 90-year-old husband, complained that Western sanctions imposed on the couple were hurting the economy.

Mugabe, his close aides and their companies have been subject to European Union and US sanctions for undermining democracy.

Once seen as a post-colonial role model, Zimbabwe's economy has been in a downward spiral since thousands of white-owned farms were seized under a controversial land reform programme in 2000.

Critics have blamed the land grabs for the economic collapse. Millions have fled the country as economic refugees.

But the first lady defended the controversial land reforms, saying: "We are just taking our property that was stolen from us by thieves."

Recently nominated to lead the powerful women's wing of the ruling ZANU-PF party, she has launched a series of campaign rallies ahead of the party's December congress where she is certain to secure the position.

She vowed on Wednesday to change the face of politics in Zimbabwe and end the factionalism threatening to tear apart the ruling ZANU-PF party as different camps feud over Mugabe's succession.

She also denounced anti-government protests led by opposition leader Morgan Tsvangirai over Mugabe's failure to revive the economy.

"You saw what happened in Libya, ... in Egypt there is no peace," she told some 4,500 supporters at a city sports centre.

Her jubilant supporters danced to music chanting slogans in support of "Dr Grace Mugabe" - a title she was controversially awarded by the University of Zimbabwe.