NAIROBI, Kenya (CNN) -- Gangs of young men armed with machetes are roaming the streets in Kenya as post-election violence threatens to engulf the country. Horrific attacks are being reported, including the torching of a church where people who had sought refuge were burned alive.
At least 148 people have been killed and about 75,000 have fled their homes since President Mwai Kibaki won a narrow victory, according to Kenyan government officials. The Associated Press reported a higher number -- about 275 -- have died since Saturday.
Much of the violence is between supporters of Kibaki from the majority Kikuyu tribe and backers of opposition leader Raila Odinga, who is from the Luo tribe.
The ethnic violence, previously rare in Kenya, is reminiscent of the strife that led to the Rwanda genocide.
In a particularly disturbing incident, a mob appears to have burned a church filled with Kenyans seeking refuge from the violence.
The Red Cross told The Associated Press that at least 50 were burned to death at the church, some of them children.
As many as 200 people were at the church, about 185 miles northwest of Nairobi, KTN reporter Tony Biwott told CNN. Watch as machete-wielding looters haul away goods »
Biwott said he counted at least 15 charred bodies, including children, in the burned church and an adjacent field.
"I'm sure there were more than 15 but I couldn't count the ones who were ashes," he said in a phone interview.
The wounded sustained gunshot wounds, burns and cuts from a panga, a machete-like weapon, the Red Cross said. Watch smoke darken skies near a burned church
The national police commissioner has said in Kenyan society, churches are considered sacred and no one would expect such violence there.
He said an investigation into the incident is under way.
About 120 people are reported dead and over 1,000 injured countrywide, according to The Red Cross.
Police and political backers of opposition leader Raila Odinga began clashing about four days ago as Odinga, of the Luo tribe, narrowly lost Kenya's presidential election to Mwai Kibaki.
Kibaki is a member of Kikuyu, Kenya's largest tribe.
Violence broke out in several cities as frustration mounted during the slow hand-count of the ballots. Kibaki was re-elected with 51.3 percent of the vote, to 48.7 percent for Odinga.
"What we now witness is a cold and calculated plan to organize and engage in massacres," government spokesman Alfred Mutua said.
Bringing in the New Year, Kibaki -- who rarely speaks to the press -- urged calm to the nation.
"It now is a time for healing and reconciliation amongst all Kenyans," he said.
Foreign Minister Raphael Tuju said the government is committed to taking control.
"If the tear gas doesn't work then unfortunately they have to use live bullets," he told CNN. "The president has been sworn in, the elections are over, the Kenyans have to accept the results, the opposition has to accept the results."
Tuesday, international observers said the balloting fell short of international standards for democratic elections.
Alexander Lambsdorff, the head of the EU Election Observation Mission in Kenya, cited discrepancies in vote counts, election observers being turned away from polling places and observers being refused entrance to the electoral commission vote-counting room.
The violence also has displaced some 75,000 Kenyans inside the country, Mutua said.
The government said Tuesday it will not allow any political rallies in the aftermath of the controversial election outcome.
Odinga's opposition Orange Democratic Movement had scheduled rallies for Tuesday, raising fears of more violence.
Mutua said there was no intention to impose a state of emergency or curfew at this point, and said police are handling the violence well and with "extreme restraint."
However, he warned that police restraint would not last forever. The violence is rare for Kenya, which has enjoyed relative calm even as war and chronic political violence wracked neighboring countries, such as Ethiopia, Sudan and Uganda.
The United States has withheld congratulations for Kibaki, citing concerns of voting problems, even though Kibaki has claimed victory. E-mail to a friend