NAIROBI, KENYA, SEPT. 3 -- The government of the small, tribally divided central African nation of Burundi was overthrown today in a bloodless military coup, Radio Burundi reported.

The broadcast said the country's leader, Col. Jean-Baptiste Bagaza, who was in Quebec at a summit of leaders of French-speaking countries, had been relieved of his duties as president, head of the ruling party and chief of the military.

Airports and land borders of the Maryland-sized country had been closed temporarily, Radio Burundi added. A night curfew was ordered and people were told to stay in their houses. Reports from diplomats in the capital of Bujumbura said the city was calm.

Bagaza, 41, who came to power in 1976 in a bloodless military coup, flew from Quebec to New York and on to Paris.

{Early Friday, Bagaza left Paris aboard an Air France 747 bound for Burundi, Reuter reported. The flight also was scheduled to stop in Nairobi and Kigali, Rwanda, and Bagaza's destination was not known.}

As the leader of a minority tribal regime, Bagaza has attempted one of Africa's most delicate balancing acts. Members of his tribe, the Tutsi, dominate the government and the military. Yet the Tutsis are outnumbered 6 to 1 by the Hutus. Hatred between the tribes is enforced by memory of genocide in 1972, when a previous Tutsi-controlled government systematically killed about 100,000 Hutus.

Radio Burundi said the government would be taken over by "a military committee for national redemption led by Maj. Pierre Buyoya."

Buyoya, a Tutsi, sits on the 50-member central committee of the ruling party. No other information was available tonight on the major. He is not one of the country's more senior military men. It was not clear whether his new military regime will want to increase Tutsi tribal control or lessen it.

As president, Bagaza tried both to heal the wounds of the '72 killing and maintain Tutsi dominance. It was a policy hobbled by contradictions. He invited home 150,000 Hutus who had fled in the mid-1970s. He forced Tutsi landlords to give farmland to Hutus, and he instituted economic changes that helped Hutu farmers and broke import monopolies held by some Tutsi businessmen.

But Bagaza made sure that 96 percent of the country's military remained Tutsi. He felt personally threatened by the powerful Roman Catholic Church, which he saw as a possible vehicle for Hutu revolt. (Nearly all Hutus are Catholic.) In the past five years, hundreds of foreign priests and nuns have been forced to leave the country. In the past year, all Catholic schools were closed and church services were banned except on Sunday.

The rapid pace of a shift to free-market economics in the past year had pleased many western donor countries. But diplomats there said in July that it also spawned rumors that senior Tutsi military leaders were unhappy with Bagaza for moving toward an economic egalitarianism that could one day undermine Tutsi dominance.

A faction of western-educated Tutsis in the government said Burundi was moving too slowly toward tribal integration.

Bagaza was a member of a minority within a minority, the southern Hima Tutsis. That subgroup controlled most of the important positions in the government and is widely resented by northern Tutsis.

Burundi has little industry. As in many landlocked countries in Africa, rapid population growth threatens to make it even poorer.

In recent years, in part because Bagaza's government had developed a reputation for honest, efficient management, Burundi became a favorite recipient of donor aid from West and East. This year it received more than $150 million.

When Burundi became independent in 1962, not one Burundian had a college education. Belgian Catholic priests controlled the education and health systems. Even into the 1980s, the Catholic Church was reluctant to give up this power.

Bagaza's repression of the Catholic Church, which he insisted was aimed at restoring the government's legitimate authority over education, provoked an angry rebuke from the Vatican.

Pope John Paul II said last fall that the crackdown, which in the past five years has reduced the number of foreign priests from 500 to about 30, "seems to indicate a deliberate attempt to discredit the church and its pastors through accusations, insinuations and threats."

Catholic leaders and human rights groups have been quick to see a connection between suppression of the church and tribal politics. Although tribal background is a key determinant of educational and career opportunities in Burundi, the Bagaza government had insisted that Burundians not talk about it.

The government declared in June that Hutu-Tutsi conflict "is nonexistent." Many people in the country are reluctant even to use the tribal names. They speak instead of "the short ones" -- the Hutus, who are mostly farmers of Bantu origin -- and "the tall ones" -- the Tutsis, who were once cattle people, probably of Ethiopian origin.