( Reuters ) - Opposition leader Raila Odinga vowed to defy police and hold a million-strong rally on Thursday against Kenyan President Mwai Kibaki's disputed re-election, which has sparked violence that has killed more than 300 people.
As crowds of opposition supporters began heading for the rally, riot police flooded central Nairobi where the protest was planned for early afternoon in Uhuru Park, which draws its name from "freedom" in Swahili. The government has banned the rally.
Police lobbed teargas at several hundred anti-government protesters chanting "Peace" as they sat down on a Nairobi highway, blocking a major roundabout, a Reuters witness said.
"We are gathering now ... The whole of Nairobi is going to go to Uhuru Park," said James Ngare, a resident of Nairobi's Kibera area, one of Africa's largest slums and a hotbed of Odinga support.
Both sides have traded accusations of genocide in a week of violence that has shocked world leaders and choked off supplies of fuel and other goods to a swathe of central Africa.
The deaths have occurred mainly in clashes between police and protesters and in fighting between different ethnic communities.
There have been international calls for reconciliation in a nation that had become known as a vibrant democracy and peacemaker in East Africa, rather than a trouble-spot.
Calling Kibaki a "thief" who had carried out "a civilian coup", Odinga told reporters he would, however, accept international mediation and proposed setting up an interim power-sharing government to prepare for a re-run of the vote.
"It should last no more than three months," he said.
"The people will not take this vote-rigging by the government lying down.
Kenya is East Africa's biggest economy and a key ally of the West in its efforts to counter al Qaeda.
In rural areas, the unrest has touched off deep ethnic tensions. In an area where 30 members of Kibaki's Kikuyu tribe were killed in a church when a mob set fire to it, young men with machetes manned roadblocks and hunted for their enemies.
The turmoil was likely to hurt tourism, Kenya's biggest earner at about $800 million a year. 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 more than 300 people had died in the violence, many victims of "bloody repression" of opposition protests.
Kikuyus, long dominant in Kenya's political and business life, were targeted in the initial clashes but revenge killings -- including some by the Kikuyu militant gang Mungiki -- are on the rise.
The government said "well-organized acts of genocide and ethnic cleansing were well planned, financed and rehearsed" by Odinga's Orange Democratic Movement ahead of the December 27 vote.
The opposition accused the government of acts "bordering on genocide" by ordering police to shoot protesters.
Foreign observers said the vote fell short of democratic standards. Local 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, smoldering 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" to end the violence, U.S. State Department spokesman Sean McCormack said in Washington.
Nobel peace 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.
The Kenyan government and religious figures urged local leaders to preach unity to ethnically polarized communities.