Zimbabwean President Robert Mugabe has threatened to retaliate against companies from Britain and the United States if the two Western powers persist with sanctions that he described as "harassment."

Mugabe's comments on Sunday follow scrutiny from outside observers of his re-election in a July vote that rival Morgan Tsvangirai denounced as a "coup by ballot" which involved alleged widespread vote-rigging.

Mugabe, who at 89 is Africa's oldest leader, has rejected the fraud allegations and was sworn in on Thursday for a fresh five-year term in the southern African nation that he has ruled since its independence from Britain in 1980.

"They should not continue to harass us, the British and Americans," he told supporters at the funeral of an air force officer.

"We have not done anything to their companies here, the British have several companies in this country, and we have not imposed any controls, any sanctions against them, but time will come when we will say well, tit for tat, you hit me I hit you."

British companies in Zimbabwe include banking groups Standard Chartered Plc and Barclays Plc. These are already the target of a so-called "indigenisation" policy that requires they cede a majority stake to black Zimbabweans.

Mugabe and prominent members of his ZANU-PF party are already the targets of financial and travel sanctions imposed by the United States and the European Union.

The controls were applied by Washington and Brussels to punish alleged election-rigging and abuses of power.

Britain said last week that Mugabe's re-election could not be deemed credible without an independent investigation into allegations of voting irregularities.

US officials also said the July 31 election was flawed and Washington had no plans to loosen sanctions until there were signs of change in the country.

In contrast, observers from the regional 15-nation Southern African Development Community (SADC) and the African Union broadly endorsed the Zimbabwean vote as free and peaceful.

Al Jazeera and wire services