A string of blasts levelled arms depots at a Tanzania military base, killing at least 20 people and leaving thousands homeless in the second such incident in two years, officials said on Thursday.

The explosions that erupted late Wednesday and lasted for the most part of the night showered shrapnel and destroyed houses in Tanzania's largest city Dar es Salaam, causing panic among residents, some of whom fled their homes.

Acting Dar es Salaam region chief administrator Said Meck Sadiq said 20 people had lost their lives in the blasts that rocked Gongo la Mboto military base in the outskirts of the city.

Prime Minister Mizengo Pinda told parliament that some 4,000 people living around the barracks were driven from their homes and took shelter at a city stadium, and that more than 140 people were also wounded.

The explosions forced the temporary closure of the airport in Dar es Salaam and another on the country's semi-autonomous Zanzibar island, a popular tourist destination.

A KLM flight carrying 300 passengers to Dar es Salaam had to be diverted to land at Kilimanjaro airport in the north of the east African country for security reasons.

Pinda said he had convened an emergency security meeting over the blasts and added that the country's armed forces were investigating the incident.

The blasts started going off at around 8:00 pm (1700 GMT) on Wednesday in one ammunition depot and quickly spread to other arms dumps in the same military base.

Two nearby residential houses and a secondary school were destroyed by the explosions, the prime minister said.

There was no indication of foul play, and such incidents have happened before in Tanzania.

President Jakaya Kikwete visited the scene and appealed for calm, saying the situation was under control

In April 2009, 26 people were killed and hundreds wounded in powerful blasts at an arms depot in Dar es Salaam, which officials said were accidental.

The 2009 blasts in the Mbagala district, located around 13 kilometres (eight miles) from the city centre, set off rockets, artillery and mortar shells, and displaced thousands of people.

The explosions brought back memories of the 1998 bombing of the US embassy in Dar es Salaam, Tanzania's commercial capital.

According to a US State Department briefing released in the aftermath of the 2009 disaster, the frequency of such incidents in arms depots across the world is increasing.

"Poorly maintained, improperly stored, or inadequately guarded conventional weapons and munitions pose as significant a humanitarian challenge as the well-known threat of landmines and other explosive remnants of war left uncleared from past conflicts," it said.

"The frequency of such incidents has increased as urban populations have expanded outward from city centers to the vicinity of what were often previously isolated depots," it explained.

The State Department estimated that such incidents resulted in more than 4,700 fatalities and nearly 5,700 injuries between 1995 and 2009.