* New law meant to address graft, tribalism, land issues
* Kenyans vote peacefully in constitution referendum
* "No" camp alleges vote rigging
(Adds 'No' camp claims vote rigged, minister quote, observers)
By Duncan Miriri
NAIROBI, Aug 4 Partial results showed two-thirds of Kenyans voted in favour of a new constitution on Wednesday in a peaceful poll that could reshape the politics of east Africa's largest economy after years of disputed, violent elections.
The constitutional changes are seen as important to avoid a repeat of the post-election tribal bloodshed in early 2008 that killed 1,300 people and pushed the country of about 40 million people to the brink of anarchy.
They address the corruption, political patronage, land grabbing and tribalism which have plagued Kenya since it won independence in 1963. The changes allow for greater checks on presidential powers, more devolution to grassroots administrations and an increase in civil liberties.
"I have come to vote for the new constitution which will guarantee me security in my farm where I was displaced in 2007 during clashes," said Milkah Gathoni Njoroge, who was born in 1919. "I am living with my family in Nakuru town. If the constitution passes, I will return to my land."
Take a Look on Kenya [ID:nLDE67008Q]
Table of provisional results [ID:nLDE67216I]
Kenya's 27,689 polling stations in 210 constituencies closed at 5 p.m. (1400 GMT) with no major incidents reported.
Some 12.5 million people were registered to vote. Of more than 5 million votes counted by 2100 GMT, 66.4 percent had voted "Yes". The final results are likely some time on Thursday.
"It does appear that 'Yes' is winning overwhelmingly ... but we should not come out of this with the division of winners and losers," Foreign Affairs Minister Moses Wetangula told Reuters at the national tallying centre in Nairobi.
"This is part of the healing process from the electoral difficulties of 2007."
Regional election observers said they were satisfied with the voting process, and called for calm during the count.
A group of "No" members of parliament and some members of the clergy said the vote had been rigged in favour of the "Yes" camp.
They were angry at the use of a new electronic system used to transmit votes from polling stations to the national tallying centre, from where they are broadcast live on television.
The complaints were brushed aside by the electoral authority which said the process was meant to improve transparency.
There were long queues at polling stations across the country, especially in the Rift Valley centres of Eldoret and Nakuru that were at the centre of the violence in 2008.
Turnout was reported to be low in the poor, arid northeast of the country.
If the law fails, Kenya will retain the current constitution bequeathed by former colonial power Britain.
William Ruto, a cabinet minister based in the Rift Valley who is leading "No" campaigners angry about clauses related to land ownership, said he would accept the outcome.
"This is an historic moment in our country and I'm sure Kenyans will make the right decision," he told reporters in his constituency. "Everyone has an obligation to accept the decision of the people of Kenya."
A previous attempt to change the constitution through a referendum in 2005 failed. To be adopted, the law requires 50 percent plus one vote of the ballot cast nationally and at least 25 percent of the votes in five of Kenya's eight provinces.
Kenyan shares rallied strongly for the fifth straight session on Tuesday to hit their highest level since Sept. 3 2008, driven by expectations the law will be adopted, while the shilling rose against the dollar.
Markets were closed on Wednesday. Traders and analysts say investors would take great confidence from the peaceful passage of the constitutional changes into law.
Kenya, which borders Somalia, Ethiopia, Sudan, Uganda and Tanzania, is the fourth largest economy in sub-Saharan Africa after South Africa, Nigeria and Angola.
Voting was peaceful in the sprawling Kibera slum in Nairobi, a hotspot of post-election violence in 2008.
In Eldoret and Nakuru, some voters said they hoped the referendum would lead to a new era of peaceful democracy and pledged an end to violence between Kikuyu and Kalenjin -- the two tribes that have dominated politics since independence.
The electoral authority said on Tuesday the process would be more transparent than the 2007 election, when allegations the poll was rigged in favour of President Mwai Kibaki sparked the bloodletting.
The new charter was a key provision in the power-sharing deal struck between then-rivals Kibaki and Prime Minister Raila Odinga to end the violence after the 2007 election. (Additional reporting by James Macharia, Duncan Miriri, Helen Nyambura-Mwaura, George Obulutsa and Humphrey Malalo in Nairobi; Richard Lough in Eldoret; Celestine Achieng' in Mombasa and Antony Gitonga in Naivasha; Writing by David Clarke; Editing by Tim Pearce)