Nigeria is marking a national day of prayer and mourning, following a series of explosions at a munitions depot that killed more than 600 people Sunday in the commercial capital, Lagos.

President Olusegun Obasanjo called the day of mourning as anger rose among Nigerians who demanded explanations for the incident, which the Nigerian leader described as a national disaster.

In remarks broadcast late Monday, Mr. Obasanjo acknowledged that about 600 people had died as a result of the blasts Sunday at the Ikeja military facility. Flags in Lagos and other cities across Nigeria, Africa's most populous country, remained at half-staff.

Witnesses say the series of explosions started with a small fire at a nearby street market that spread quickly into the munitions depot. The explosions that followed sent burning shrapnel flying into adjacent homes and businesses. Panicked residents ran for their lives.

People's anger has been fueled by images on television and in newspapers of workers pulling hundreds of bodies from the Oke-Afa canal.

The cadavers are those of people, many of them children, who plunged into the canal and drowned as they tried to run from the blasts. Witnesses say victims got caught in the crush and were pushed into the canal by those running behind them.

The Nigerian Red Cross says thousands of people remain listed as missing. Relief workers are also trying to reunite at least 300 children who lost contact with their parents during the explosions Sunday.

Residents are demanding answers as to why the military was storing large amounts of high-power explosives in a facility in the Ikeja district, a densely populated area of Lagos.

Military officials say there had been safety concerns raised earlier about the way the ammunition was being stored at the Ikeja military facility. For now, officials are calling for Nigerians to avoid speculating on who is to blame until the investigation is complete.