Blasts rung out across the southern Yemeni city of Aden when a series of explosions caused by heat and friction rocked a military weapons storehouse, a local official said.
Witnesses said the blasts lasted for up to 45 minutes and blew out the windows of a neighbouring mosque and three houses. Two of the houses also caught fire.
There were reports of casualties several hours after Wednesday's explosions.
A black column of smoke rose from the site of the explosions as ambulances, fire engines and army vehicles rushed to the area. Security forces sealed it off, congesting central Aden during the evening rush hour.
Yahya al-Quhlani, governor of Aden province, told journalists that old munitions had exploded, adding that initial investigations showed the blasts were caused by friction or heat.
A senior military official in Aden confirmed that the warehouse was used to store old, unusable munitions. He spoke on condition of anonymity because he was not authorized to give statements to the press.
Areas in the centre of the city quickly became congested as security forces sealed off the immediate area called Jabal Hadid.
Aden, 330 kilometres south of the capital Sana'a, is the economic capital of Yemen. It was the site of the October 2000 of the USS Cole that killed 17 sailors and was blamed on Al-Qaeda.