It has already hit financial and commodity markets in the tea- and coffee-growing nation.
The shilling currency dropped to a six-week low. Stocks also fell, while commodities auctions were postponed.
A local and an international rights group said many of the dead were victims of "bloody repression" of opposition protests.
Kikuyus, long dominant in politics and business, were targeted in initial clashes but revenge killings -- including some by the Kikuyu militant gang Mungiki -- are on the rise.
The government said "well-organised acts of genocide and ethnic cleansing were well planned, financed and rehearsed" by Odinga's Orange Democratic Movement ahead of last week's vote.
The opposition accused the government of acts "bordering on genocide" by ordering police to shoot protesters.
Observers said the vote fell short of democratic standards.
Uganda's President Yoweri Museveni became the first African leader to send congratulations to Kibaki.
Silence by most of the continent's leaders has underlined concerns about alleged rigging.
The only other country to congratulate Kibaki has been the United States, within hours of his swearing-in on Sunday. But since then, U.S. officials have pointedly declined to repeat that endorsement and instead expressed concern.
Kenyan media united in pleas for peace, with every major newspaper running the same front-page headline: "Save Our Beloved Country".
"Kenya is a burnt-out, smouldering ruin. The economy is at a virtual standstill and the armies of destruction are on the march," said the Nation.
"In the midst of this, leaders -- who are the direct cause of this catastrophe -- are issuing half-hearted calls for peace, from the comfort of their hotels and walled homes in Nairobi, where they are conveyed in bullet-proof limousines."
International efforts to mediate have been stepped up.
U.S. Secretary of State Condoleezza Rice was phoning Kibaki and Odinga to urge both to "do everything they possibly can in the name of political reconciliation", a spokesman said.
South Africa's Nobel Peace Prize laureate Archbishop Desmond Tutu was due to meet the head of Kenya's electoral commission on Thursday. Ghanaian President John Kufuor was waiting to talk to Kibaki before deciding whether to visit Nairobi himself or send a team.
