Robert Mugabe is at it again. The 87-year-old dictator is shaking his fist and threatening that his regime will seize all foreign owned companies.

In response to U.S. President Barack Obama's renewal of travel and financial sanctions against him and 200 of his closest associates, Mugabe held a rally in Harare to denounce the measures, according to GlobalPost's correspondent in Harare. Before a crowd of about 30,000 supporters, bussed in to the rally, Mugabe threatened to seize foreign firms and boycott their products in retaliation for Western sanctions against him and senior members of his ruling Zanu-PF party.

Although the sanctions are against Mugabe personally and his family and closest cronies, the Zimbabwean president blames them for Zimbabwe's economic decline. At the rally Mugabe gave a lengthy speech in which he said the sanctions are hurting all Zimbabweans.

Mugabe specifically threatened British banks and businesses, saying they controlled 400 businesses in the former British colony in southern Africa.

"It is now time to take action," Mugabe told thousands of supporters at the outdoor rally, reported Al Jazeera. "Indigenization and empowerment should start with those companies. We must take them over. We are not ashamed of that."

Mugabe launched a campaign to gather 2 million signatures — from a population of about 13 million — to protest the sanctions. Among those signing at the rally were cabinet ministers, judges and army generals.

The European Union and the U.S. imposed a travel ban and financial sanctions on Mugabe and his Zanu-PF cronies over documented human rights abuses dating back beyond 2000 as well as election fraud. Mugabe however insists the sanctions were imposed because he seized land belonging to white Zimbabwean farmers.

Mugabe charged that British firms and other European and American interests earned unfair profits on mining and other ventures.

"We say no to that. If we know that some of them have products which we are buying, including foodstuffs, before we seize those companies, we can boycott their products," he said.

Mugabe has said previously Zanu-PF will nationalize firms from countries that have imposed sanctions, arguing they should not operate freely while Western powers punish his party.

The threats heightened worries of foreign investors in the resource-rich country, which introduced a law specifying 51 percent of firms worth over $500,000 should be owned by black Zimbabweans. The law was passed in March 2010 but has not yet been implemented by the Mugabe regime.

The threat of nationalization has choked fresh foreign investment in Zimbabwe's struggling economy. For instance, Zimbabwe has the world's second largest deposits of platinum, yet most mining firms are holding back on investing because of Mugabe's threats of nationalization, reports the Wall Street Journal.

Between 2000 and 2008 Zimbabwe's economy shrank by more than 50 percent, a contraction that the World Bank said was unprecedented for a country not at war. Zimbabwe's once busy factories are now operating at 30% capacity as a result of the economic downturn and because of lack of lending and the reluctance of foreign firms to invest in their Zimbabwe subsidiaries.

In the past two years Zimbabwe's economy has posted positive economic growth, with 8.1 percent in 2010 compared with 5.1 percent in 2009, thanks to a confidence-building political settlement and the introduction of the U.S. dollar as an official currency. Officials and economists say the growth would have been far higher without the controversy around the indigenization law.

"Industry is suffocating," said Joseph Kanyekanye, president of the Confederation of Zimbabwe Industries.

Mugabe's rally was boycotted by Prime Minister Morgan Tsvangirai and his opposition party, the Movement for Democratic Change. The MDC, currently in a shaky coalition with Mugabe, said the international sanctions against Mugabe and his Zanu-PF party are a result of its record of violence, intimidation and vote-rigging. Tsvangirai criticized Mugabe's party as "unpopular and bloodthirsty."