At least 20 people have been killed and more than 600 wounded in a huge series of explosions at a military barracks in Equatorial Guinea.

The blasts were due to the “negligent handling of dynamite”, according to a statement from the president, Teodoro Obiang Nguema Mbasogo. He said the explosions took place at 4pm in the barracks in the neighbourhood of Mondong Nkuantoma in Bata. He said the impact had damaged almost all the buildings in the country’s main city.

The defence ministry released a statement saying that a fire in a weapons depot in the barracks caused the explosion of high-calibre ammunition. It said the provisional toll was 20 dead and 600 injured, adding that the cause of the explosions will be fully investigated.

State television showed a huge plume of smoke rising above the site of the blast, thought to be from at least five explosions, as crowds fled, with people crying out: “We don’t know what happened, but it is all destroyed.”

The health ministry tweeted that workers were treating the injured at the site of the tragedy and in medical facilities, but feared people were still buried under the rubble.

The president’s jet-setter son, Teodoro Nguema Obiang Mangue, vice-president with responsibility for defence and security, appeared in television footage at the scene of the blasts inspecting the damage, accompanied by his Israeli bodyguards.

Teodorin, as he is known, is increasingly seen as the president’s designated successor in the oil-rich Central African nation.

Bata is the largest city, with around 800,000 of the nation’s 1.4 million population living there – most of them in poverty. While it sits on the mainland, the capital Malabo is on Bioko, one of the country’s islands off the West African coast.

Equatorial Guinea has been ruled by 78-year-old Obiang Nguema for nearly 42 years. Opposition figures and international organisations regularly accuse him of human rights abuses.

A doctor calling in, who went by his first name, Florentino, said the blasts were a “moment of crisis” and that the hospitals were overcrowded. He said a sports centre set up for Covid-19

Following the blast, the Spanish embassy in Equatorial Guinea recommended on Twitter that Spanish nationals “stay in their homes”.