The United States led international pledges of emergency aid to Congo after huge blasts at an arms depot in Brazzaville killed more than 150 people and left 1,000 injured.

President Denis Sassou Nguesso announced a curfew in the capital and cordoned off the area around the devastated eastern district of Mpila, as Congo issued a plea for international help on Monday.

The government said an electrical short-circuit likely caused a fire which triggered a series of blasts so powerful they destroyed scores of houses and even blew out windows in Kinshasa, the capital of the neighbouring Democratic Republic of Congo situated across the Congo river.

Soldiers combing the wreckage of homes in Mpila recovered more bodies Monday, an AFP correspondent at the scene said, amid fears the toll will rise further in the densely populated area.

"We have more than 150 people dead, which is a provisional figure.... We have more than 1,000 injured," Interior Minister Raymond Mboulou told AFP.

The minister described the scenes of devastation in the streets surrounding the military barracks as "a tsunami without water".

The United States promised to rush emergency aid to the country.

"We are obviously saddened by the loss of life and damage caused by Sunday's explosion at the munitions depot in Brazzaville," State Department spokeswoman Victoria Nuland said.

"We are in the process of issuing a disaster declaration so that we can provide assistance and emergency help," she said.

"And we're working with the government of the Republic of Congo and the international community to determine what additional assistance might be necessary," she added.

The Democratic Republic of Congo announced it was sending 20 medical specialists across the border, as well as equipment and medication.

DR Congo Foreign Minister Alexis Thambwe Mwamba and Health Minister Victor Makwenge Kaput will also visit Brazzaville "to express our solidarity and our compassion to our brothers and neighbours" government spokesman Lambert Mende told AFP Monday.

France and Morocco said they would also send emergency medical aid, while the World Health Organisation (WHO) and Medecins sans Frontieres (Doctors without Borders - MSF) were also active.

UN chief Ban Ki-moon said he was "profoundly saddened by the loss of human life" and said the world organisation would help with recovery efforts.

A military source in Brazzaville warned that a second munitions dump 100 metres (yards) from the one destroyed, remained at risk because of nearby fires.

Thousands of people thronged Mpila's streets, picking over what remained of their homes and looking for relatives.

On Sunday, Sassou Nguesso said that the military would in future be obliged to relocate their barracks outside the capital.

The stench of decomposing flesh drifted over the area as ambulances and hearses lined up to take away the dead.

One resident told AFP earlier that a church had collapsed while people were inside attending a Sunday service.

Authorities opened two churches and a covered market to house thousands of people left homeless by the disaster.

"I lost everything. I haven't anything left. But I thank God because I'm alive," said Patricia Inopomis, a city employee whose seven children also survived.

The French ambassador in Brazzaville, Jean-Francois Valette, told AFP that the authorities estimated 3,000 people had been left homeless by the disaster.

Leger Mokeme's home, situated 300 metres from the munitions warehouse, was in ruins.

"I've lost it all. I don't know where my family is going to sleep. We were sleeping when it began. Everything has collapsed. Look, it's all gone, there's only clothes left," he said.

Congolese television on Monday sought to reunite dozens of children separated from their parents in the panic that followed the explosions.

It showed a group of about 20 children in a TV studio and appealed to anyone recognising them to get in touch with the station.

Brazzaville's hospitals have been overwhelmed by the influx of victims, with hundreds of injured crowded into wards and corridors.

News reports said that at least six Chinese construction workers were among the victims.