The Southern African Development Community (SADC) said political leaders should agree to a negotiated settlement after opposition leader Felix Tshisekedi was declared winner of the December 30 poll, to widespread surprise.
Another opposition candidate and former oil executive, Martin Fayulu, had been seen as the clear frontrunner and has appealed to the Constitutional Court to annul the result and have a recount.
It had been hoped that the vote to replace long-time President Joseph Kabila would see the first peaceful transition of power in DRC since independence from Belgium in 1960.
But sporadic outbreaks of post-election violence in the vast country -- roughly the same size as Western Europe -- has left observers concerned the unrest could escalate into a wider conflict.
The electoral commission CENI last Wednesday announced that Tshisekedi had won with 38.57 percent of the vote, while Fayulu came second with 34.8 percent.
Former interior minister Emmanuel Shadary -- Kabila's chosen successor -- came third.
The election, originally due in late 2016, finally went ahead after numerous delays despite organisational concerns, controversy over voting machines, insecurity and an Ebola outbreak.
On Sunday, the SADC urged "all political leaders to consider a negotiated political settlement for an all-inclusive government" in the sprawling central African country.
Zambian President Edgar Chagwa Lungu, whose country currently holds the rotating presidency of the 16-member SADC, said such a move would "enhance public confidence, build bridges and reinforce democratic institutions of government and the electoral process for a better Congo".
Lungu has spoken to Tshisekedi and "other stakeholders within and outside of the DRC", the SADC said in a statement.
Noting "strong doubts" over the results voiced by DRC's powerful Roman Catholic Church -- which had deployed more than 40,000 poll monitors -- as well as Fayulu's camp and other observers, SADC said it "feels a recount would provide the necessary reassurance to both winners and losers".
SADC includes South Africa and Angola, which have economic interests in DRC.
Several Western governments have expressed concern about the results, with the United States calling for "clarification".
The European Union on Thursday said it was waiting for "the reactions of different observation missions that have observed the elections."
On Sunday, Fayulu attended a Protestant church and told his supporters that "the people have decided and the will of the people will be realised".
Parishioners greeted his words with an amen.
He has said that if Tshisekedi becomes president "he will be Mr. Kabila's stooge who will continue to pull the strings".
Analysts have said it was likely Kabila struck a deal with Tshisekedi to be declared the election winner.
Kabila has been in office for 18 years, taking over the presidency from his father after he was assassinated.
A long-running political crisis erupted two years ago when Kabila refused to step down at the end of his constitutional term in office, sparking massive protests which were brutally repressed.