Members of Zimbabwe's opposition say they have been targeted by Mugabe supporters following the president's re-election.
President Robert Mugabe's declaration as winner has been met by international concern over the conduct of the African nation's poll.
Robert Mugabe has secured his grip on power in Zimbabwe today after his party ZANU PF won a majority in parliament in Wednesday's election.
Botswana's government has disputed the result of Zimbabwe's general election which saw the long-standing president Robert Mugabe claim a landslide victory.
Its assessment stands in stark contrast with that of South Africa, which has congratulated Mr Mugabe on his victory.
Both nations belong to the Southern African Development Community which monitored the vote, and now appears to be divided.
The Botswana government said that although the election day itself had been "free of overt intimidation and violence", the electoral process "cannot be considered as an acceptable standard for free and fair elections".
Zimbabwe's main stock market index fell 11 percent on Monday in its first trading day since official results confirmed President Robert Mugabe would extend his 33 years in power.
The industrial index fell to 205.57 points in the mid-morning session, with all the top-ten shares save for the local unit of insurance giant Old Mutual trading in the red.
Young Zanu-PF supporters from the Mbare area of Harare, Zimbabwe have been celebrating in the streets following Robert Mugabe's victory in the country's presidential election.
The president of South Africa has congratulated Zimbabwean leader Robert Mugabe on his re-election.
Jacob Zuma's approval is in sharp contrast to Western governments which questioned the credibility of a rushed, disputed vote.
African monitors broadly approved the conduct of the Zimbabwe election, but Mugabe's main rival, Movement for Democratic Change (MDC) leader Morgan Tsvangirai, has said he will challenge the results in court with evidence of massive vote-rigging, irregularities and intimidation.
One of Zimbabwe's leading Sunday newspapers has reported that President Mugabe "romped" to victory in the country's election.
The Sunday Mail is part of a group of newspapers owned by the government and has been criticised by the opposition for its support of Zanu-PF.
US Secretary of State John Kerry says the United States does not believe that the Zimbabwean election results announced today "represent a credible expression of the will" of its people.
Read more: Mugabe wins Zimbabwe election
Foreign Secretary William Hague commended the people of Zimbabwe for holding peaceful presidential polls, but voiced "grave concerns" about the conduct of the election, which delivered Robert Mugabe a further term in power.
People around the world are watching events in Zimbabwe, following the announcement by the Zimbabwean Electoral Commission that President Mugabe has won the presidential elections, as well as the indications of possible legal challenges.
I commend the people of Zimbabwe on holding peaceful elections. However we have grave concerns over the conduct of the election.
The preliminary statements of the African Union (AU) and Southern African Development Community (SADC) observation missions, and those of the domestic observer groups, have outlined many of these significant concerns, and I hope that their final assessments of the elections will take into account the full impact of these irregularities on the outcome.
Zimbabwe's President Robert Mugabe has won re-election for another five-year term, scooping up 61% of the votes.
The country's main opposition leader Morgan Tsvangirai gained 33.9% of the overall votes.