BBC News, Harare
It was an unexpected early morning national address, some say damage control prompted by growing global criticism.
The president's tone was part conciliatory, calling for patriotism, assuring the nation that political and economic goals are on course.
But it was the warnings that worried some. President Mnangagwa spoke of "dark forces" from within and outside, opposition terrorist groups, and flushing out "bad apples".
It is raising concerns about repression.
Many have already been arrested for demonstrating against corruption. The Hashtag #Zimbabweanlivesmatter is trending globally in solidarity.
Zimbabwe’s economy has been on the slide, which the government blames on acts of economic aggression, currency manipulation and Western sanctions.
Zimbabwean's President Emmerson Mnangagwa has given a stark warning to opposition figures and human rights campaigners amid growing uproar over corruption and economic mismanagement.
In a televised address on Tuesday, the president condemned the "machinations of destructive, terrorist opposition groupings".
"Those who promote hate and disharmony will never win. The bad apples that have attempted to divide our people and to weaken our systems will be flushed out. Good shall triumph over evil," he said.
Opposition supporters and activists had last week called for anti-government protests, but security agencies ordered people to stay indoors. Some activists including Booker-longlisted author Tsitsi Dangarembga were arrested and later released on bail.
Zimbabwe Lawyers for Human Rights say more than 60 people have been detained.
Mr Mnangagwa in his speech said "security services will continue to carry out their duties with appropriate astuteness and resolve".
"We shall overcome attempts at destabilisation of our society by the few rogue Zimbabweans acting in league with foreign detractors," he said.
Here is a video clip of President Mnangagwa's speech:
The world through its media
About 20,000 people have reportedly unfollowed Zimbabwe's President Emmerson Mnangagwa on Twitter in protest against his government.
According to the private ZimLive website, opposition activists started a "peaceful resistance" campaign last week to unfollow the president, decrying a deepening economic crisis in the country.
According to the website, the president's Twitter followers were down from 565,000 to 546,000 by 4 July.
Mr Mnangagwa’s spokesman George Charamba dismissed the move, saying the president was not concerned by "fake people" unfollowing him.
It comes as the opposition and civil society groups are mobilising for nationwide protests on 31 July to demand that President Mnangagwa step down. Security forces have previously clamped down on protests.
By Andrew Harding
Africa correspondent, BBC News
By Shingai Nyoka
BBC News, Harare
Zimbabwe's First Lady Auxillia Mnangagwa has asked manufacturers and retailers to lower prices of food and basic commodities, the state-run Herald newspaper reports.
Mrs Mnangagwa reportedly urged the traders to consider the plight of low-income earners.
"I implore all of us to continuously work on our pricing models so that they are reflective of the poor, whose right to food security remains paramount. Let us improve access to basic commodities to the marginalised, while ensuring that your businesses remain viable," she said at the the annual retailers and manufacturers awards.
The first lady said she was aware of the high cost of production in the country.
"I am aware of the challenges business is facing like foreign currency, load-shedding, fuel situation and high cost of rentals," she is quoted as saying.
Around a half of the country's population is facing hunger, with 7.7 million reported to be experiencing severe hunger.
The UN has already announced that it will provide food aid to 4.1 million of those facing hunger.
Zimbabwe was once a major food producer in southern Africa but is currently in the middle of a drought and inflation that have both adversely affected food production.
President Emmerson Mnangagwa government plans to scrap its plan to remove grain subsidies next year, a move it says will protect impoverished citizens from rising food prices, state media reported last month.
BBC Africa, Harare
Zimbabwe's President Emmerson Mnangagwa arrived in parliament for his state of the nation address in a gleaming vintage Rolls Royce, accompanied by horses.
None of the pomp and ceremony could persuade the main opposition Movement for Democratic Change (MDC) to stay. The party does not recognise his presidency, accusing him of stealing last year’s vote.
In a 40-minute conciliatory speech, Mr Mnangagwa admitted the need to address concerns about the elections in order to deepen democracy.
While he highlighted the positives of the last year - a budget surplus, wage increases for civil servants and renewed diplomatic talks with the European Union - he ignored the elephant in the room, soaring inflation and rising discontent that threatens to destabilise the southern African nation.
Zimbabwe's main opposition party walked out of parliament as President Emmerson Mnangagwa began his state of the nation address.
A spokesman for the Movement for Democratic Change (MDC) said the party does not recognise Mr Mnangagwa as a legitimate president, a news site has tweeted:
In his address, Mr Mnangagwa urged all opposition parties to join a national dialogue which began after the disputed 2018 elections.
He also asked people to be patient as the government implements reforms aimed at addressing the country's economic challenges.
A severe cash and fuel shortage, high levels of inflation as well as power cuts are making life extremely difficult for Zimbabweans.
The MDC's attempts to organise protests against the government's handling of the economy have been repeatedly broken up by the police.
Mr Mnangagwa's victory in elections was marred by allegations of vote-rigging, and at least six people were killed at the time in clashes between the security forces and opposition supporters.
Zimbabwe's President Emmerson Mnangagwa, who was once Robert Mugabe's mentee before the pair became bitter political rivals, has given a statement in Harare.
"On behalf of our nation... I wish to express my deepest, heartfelt, condolences to the Mugabe family," he said.
"He has imparted to our nation a lasting lesson in devotion, love and care. We join here in grief, loss and bereavement.
"The Zanu-PF party has met and we have accorded him national hero status, which he richly deserves.
"We declare days of mourning until he is buried."