Observers from the Commonwealth have condemned the Zimbabwean army's deadly use of force to break up protests in Harare by opposition supporters who claime a presidential election was rigged by the ruling party.
Former colonial power Britain also said it was deeply concerned by the situation, while the United Nations had earlier called from restraint from all sides in the bloody aftermath to Monday's election.
President Emmerson Mnangagwa meanwhile said he had been talking to opposition leader Nelson Chamisa to try to defuse tension after clashes on the streets of Harare in which troops opened fire on opposition demonstrators, killing three.
The streets were calm on Thursday morning although many shops were shuttered in the city centre.
But the dispute over the conduct of the elections and subsequent violence has punctured the euphoria over the army's removal of longtime strongman Robert Mugabe last November and the hope that Zimbabwe might be entering a new era of democracy after decades of political repression and economic ruin.
The international community's view on the election is crucial to Harare's efforts to patch up relations after years of hostility under Mugabe and secure the billions of dollars of donor funding and investment needed to rebuild its economy.
But observers from the Commonwealth, the group of mainly former British colonies that Mnangagwa had been hoping to rejoin, did not mince their words.
"We categorically denounce the excessive use of force against unarmed civilians," former Ghanaian president John Mahama said in a statement on behalf of the Commonwealth.
The Commonwealth also urged the Zimbabwe Electoral Commission to expedite the announcement of the results of the presidential vote. The observers had on Wednesday reported a number of problems with the poll, inlcuding voter intimidation.
A British Foreign Office minister, Harriet Baldwin, urged political leaders to ensure calm and restraint.
The European Union said the elections were competitive and freedoms were respected, but that there was a lack of a "truly level playing field".
Writing on Twitter, Mnangagwa also called for an independent investigation into the violence and offered his condolences to the families of victims.
He said he had been in contact with Chamisa. But there was no response from the MDC Alliance leader, who claimed several times on Twitter to have "won the popular vote" but provided no numbers or concrete evidence of fraud by the ruling ZANU-PF party.
The deployment of soldiers and their shooting and beating of unarmed protesters is likely to set back efforts to end the pariah status that Zimbabwe acquired in the latter half of Mugabe's nearly four decades in charge.
In particular, it is likely to confirm suspicions that the generals who ousted Mugabe - including army chief-turned vice-president Constantino Chiwenga - remain the pre-eminent political force.
"The unmeasured military response bears witness to a security apparatus little reformed since the Mugabe era," said Christopher McKee, chief executive of political risk consultancy PRS Group.
China, an important source of funding under Mugabe and Mnangagwa, said however, it believed the election had generally proceeded in an orderly fashion.