NAIROBI, Kenya (CNN) -- Ethnic fighting once again engulfed Kenya's western Rift Valley on Sunday as witnesses and Red Cross officials reported brutal attacks by members of President Mwai Kibaki's Kikuyu tribe on other ethnic groups.
The violence spread to the Rift Valley town of Naivasha on Sunday, where the Red Cross said there were reports of people being burned alive in their homes. Kenya's main opposition party and the Red Cross said as many as 30 people were killed.
Ethnic killings continued in the nearby Rift Valley town of Nakuru, where another 47 people have died since the latest wave of violence began on Thursday, according to the opposition Orange Democratic Movement.
The opposition death toll is much higher than police figures, which do not include Sunday's violence in Naivasha. Police say 31 people have died in the Rift Valley region since last Thursday. Watch CNN's Zain Verjee report on the violence »
In a statement released Sunday, ODM leader Raila Odinga condemned reports of 30 people being burned alive in their Naivasha homes and blamed the Kibaki government for fomenting the violence in the region.
"I condemn this murderous and evil act in the strongest terms possible," he said.
"What is now emerging is that criminal gangs, in a killing spree, working under police protection, are part of a well-orchestrated plan of terror."
It is a dramatic turn of events, considering Odinga was shaking Kibaki's hand three days ago after the two met under the auspices of former United Nations Secretary-General Kofi Annan.
Many had hoped Thursday's meeting, arranged by Annan who is mediating peace efforts, would bring an end to the outbreak of bloody ethnic battles that followed last month's contested presidential vote.
But it seems to have had the opposite effect.
"After stealing the elections from Kenyans, Kibaki now wishes to deny them justice and peace," Odinga said.
A Red Cross official said the agency had received reports of a non-Kikuyu family burned to death in their house in Naivasha.
Television footage showed a man in the back of a police vehicle covered in blood with a large machete wound on the side of his head. Kenyan police dispersed large gangs and cleared rocks littering the streets of the lakeside town, which is dominated by Kikuyu.
Tree branches, heavy boulders and oil drums littered the streets of Naivasha's town center as the Kikuyu gangs erected temporary road blocks, CNN correspondent Zain Verjee reported. She said the atmosphere was tense as the gangs checked cars to identify rival tribes.
Verjee said there was a heavy police presence on the outskirts of the town. Some shops remained open but the town center was almost deserted except for the roaming gangs.
It was a similar situation in Nakuru on Sunday, where ODM member the Rev. Mike Brawan said members of the Kikuyu tribe "are flushing out the non-Kikuyus from their houses."
He said Kikuyus are going house-to-house, attacking civilians who are not members of the tribe, as well as looting and burning their property. Police, he said, "are not doing much."
Brawan said he saw homes burned and people hacked to death in the violence.
"They just die with a lot of pain," he said.
It is estimated -- depending on the source -- that between 500 and 1,000 people have been killed in the violence that followed the December 27 election in which Kibaki kept his post.
Odinga, the OMD candidate for president, and his supporters claim the election was rigged. International observers noted some irregularities in the voting.
CNN's Zain Verjee and Stephanie Halasz contributed to this report.