KAYANZA PROVINCE, Burundi -- The killers came at midnight across the steep green tea fields to Isaie Minani's village.
A grenade tossed in his front window killed his 4-year-old son. Mr. Minani and his wife escaped into the darkness. For the next two hours they hid while the attackers raided more homes, shooting and knifing 25 more relatives to death.
Mr. Minani, a 35-year-old farmer dressed in rags, said they died because of his politics. A member of the Hutu tribe, he campaigns for the party that ended decades of rule by the minority Tutsis last year.
They are the same two groups that have fought a genocidal civil war in neighboring Rwanda. And all that now holds Burundi together is a balance of terror: bands of ethnic killers, an army loyal to the minority tribe and a society so divided that people get killed for venturing into the wrong neighborhood.
"The common enemy is fear," said Ahmedou Ould-Abdallah, a United Nations envoy in the capital, Bujumbura. "People are tired of it, but they are hostage to it."
In the past three months, terrorists have thrown grenades into the capital's food market three times and armed gangs have slain hundreds of poor people in the countryside. More than 20 were killed in ethnic clashes in the capital this week.
"I am very afraid to work here," said Salvator Nsengiyumva at the Bujumbura market. Two hours earlier a grenade blew up 100 feet from his bean and rice stand, killing five people.
The terrorists are on both sides of the ethnic divide, trying to destroy compromise.
In September, the mainly Hutu Frodebu party and the Tutsi-dominated Uprona party agreed to share power under a Hutu president, Sylvestre Ntibantuganya. Uprona now is threatening to withdraw because the newly elected head of Parliament had last year broadcast radio messages encouraging people to kill Tutsis.
But the strife predates political parties:
Before colonialism, Tutsis were the lords in a feudal society, trading land for crops and labor with Hutus, who make up 85 percent of the population. The Belgians, who ruled Burundi and Rwanda together, widened the class division by making Tutsis perform unpopular jobs.
Then, in 1959, three years before the two countries gained their independence, Hutus in Rwanda overthrew their Tutsi rulers, killing tens of thousands.
For the Tutsis in Burundi's army, the violence in Rwanda was used to justify stiffer repression of Hutus. Tutsis purged Hutus from the army and executed dozens of suspected coup plotters.
In 1972, the Hutus in Burundi rebelled and killed thousands of Tutsis before the army retaliated.
But in 1993, ethnic peace at last seemed possible. Burundians elected the country's first Hutu president. The defeated Tutsi incumbent stepped down peacefully. Hutus took top spots in the Cabinet. The new president, Melchoir Ndadaye, hired more Hutu civil servants.
But then, four months after the elections, Tutsi soldiers killed the Hutu president, the top two Parliament officials and three Cabinet ministers.
The assassinations brought Burundi's worst violence since 1972. Hutus hacked Tutsis to death and burned down their homes. The Tutsi-led army fought back with equal brutality. At least 600,000 of Burundi's 5.6 million people became refugees. Another 100,000 died.
The murdered president's successor died in a still-unexplained plane crash, the same crash that killed the president of Rwanda and ignited the season of killings there.
And the violence has never stopped.
In September, a Tutsi army unit visited Kamenge, a slum of Bujumbura where many Tutsis were slain in 1993. Soldiers rounded hundreds of people into a stadium while they searched their houses for guns.
Ten Hutus were loaded into an army truck bound for a police post for questioning. It never arrived. Instead soldiers drove to a field near the airport and killed their prisoners.
"If the officers wanted to know who did it, they could easily find out," said a worker at the U.N. Center for Human Rights.
So distrusted is the Tutsi-led army that many Hutu politicians insist on Hutu soldiers as bodyguards.
Planning Minister Emile Ntanyungu, a Hutu, was in the hospital Nov. 10 fighting an illness. Two men strolled past the soldiers guarding the front door, walked into his room, and shot him to death. They also killed his 19-year-old son, who was sleeping in the adjacent bed.
"When someone kills a Hutu, soldiers go laughing," said Celestin Kabura, a Hutu corporal who joined the army in 1989. "They don't bother catching them."
The Tutsis see the army as their only protection. In the north, more than 100,000 Tutsis are living in refugee camps, after fleeing from Hutu killers during 1993.
And the genocide in Rwanda compounded Tutsi fears.
"If the army does not stay mainly Tutsi," said Fabien Ngendakuhana, a Tutsi doctor in Bujumbura, "then the Hutus who want to kill us can do it."