BRAZZAVILLE, Republic of Congo - Homes and buildings collapsed in the Congolese capital after an arms depot exploded Sunday, killing at least 206 people and entombing countless others in crushed structures including inside two churches that buckled while parishioners were celebrating Mass, officials and witnesses said.

The shock waves shattered windows in a five-kilometre radius surrounding the barracks storing the munitions, including across the river that separates Brazzaville, the capital of the Republic of Congo, from Kinshasa, the capital of the larger Central African nation of Congo. Government spokesman Bienvenu Okyemi blamed a short-circuit for the fire that set off the successive blasts.

"It's like a tsunami passed through here," said Christine Ibata, a student. "The roofs of houses were blown off."

Some 1,500 people were injured, Okyemi said on national radio.

The register of a morgue in Brazzaville already had 136 bodies Sunday afternoon, as more continued to arrive. A doctor at the capital's military hospital who asked not to be named because he was not authorized to speak to the press reported 70 more deaths.

Okyemi put the official toll at 146 dead, at a late-night news conference, but said rescue workers still were looking for corpses.

He said the main fire was under control, though some homes still were burning.

President Denis Sassou-Nguesso toured two hospitals and a morgue as injured people were being brought in including a 4-year-old boy who had lost his leg. The president was visibly moved, and in a statement read on state TV he said, "We have no less than 100 dead, many wounded and significant structural damage."

The president said that the government was doing it all it could to launch a rescue effort.

"We are trying to organize ourselves. I am asking the population to show courage and solidarity. ... All the material and human loss will be evaluated and the government will take a just decision," Sassou-Nguesso said. "This tragedy is an accident."

Okyemi said the government has decided to move all barracks outside the capital. There are at least five military camps in Brazzaville.

He also announced a curfew for a perimeter around the affected area, but did not specify the area or the hours.

And he said the government is taking temporary charge of the many children found wandering around alone, apparently separated from their parents in the chaos.

It's unclear what started the fire at the tank regiment's barracks located in the capital's densely populated northern neighbourhood of Ouenze, but an official at the president's office said the depot is used to store war-grade weapons including mortars. The first blast went off at around 8 a.m., and several smaller blasts were heard throughout the morning. Another major explosion went off at around 1 p.m.

Residents woke up thinking that either an earthquake had hit them, or else a coup was under way in this nation that suffered through a 1997 civil war. Defence Minister Charles Zacharie Boawo appeared on national television to urge calm in Brazzaville and in the neighbouring capital, Kinshasa.

"The explosions that you have heard don't mean there is a war or a coup d'etat," he said. "Nor does it mean there was a mutiny. It is an incident caused by a fire at the munitions depot."

Didier Boutsindi, an official in the president's office, said the explosion woke him "with the force of an earthquake." Doors in his house, located several miles (kilometres) away from the epicenter of the blast, were thrown open and several windows cracked. He began making calls, and when he realized the origin of the explosion, his first thought was his uncle, whose home is located just next to the depot.

"The house fell completely," Boutsindi said. "He was sleeping. His wife was at church. His children -- small children -- were playing outside," he said. "The neighbours dug out the body and brought him to the morgue."

The uncle's body was among the countless others that were being brought in by car, on stretchers, and carried by shell-shocked residents. The death toll is expected to rise, Boutsindi said, as many more people remained trapped inside crushed structures, including the faithful of the St. Louis Catholic Church, who were attending Mass when the blasts began at the barracks across the road. A smaller evangelical church also fell to the ground, witnesses said, burying its parishioners.

The explosions caused buildings to shake as far away as Kinshasa, separated from Brazzaville by the 3-mile-wide (4.8-kilometre-wide) Congo River. An enormous plume of smoke could be seen snaking across the sky.

Patients crowded into hospitals, some with torn clothes and shocked expressions. Some lay on the floor as medics struggled to treat the crowd.

France, the former colonial power, is sending a shipment of emergency aid to Brazzaville after the explosions, Foreign Minister Alain Juppe said in a statement Sunday. Condolences began arriving from around the world.

"I was greatly saddened to hear of the large number of casualties in the explosions which occurred in Brazzaville today," British Foreign Secretary William Hague said in a statement. "Our thoughts are with the families."

Among the dead were Chinese workers working of a company located near the depot that was building low-income housing.

The official Xinhua News Agency quoted Chinese Embassy officials as saying three Chinese workers were killed and dozens were injured in the explosions. Xinhua said the dormitory building of Huawei Technologies Ltd, China's largest maker of telecommunications equipment, was badly damaged.