Nigeria’s president has announced an immediate two-week lockdown in Kano, the largest city in the north, after local reports of a big rise in deaths in recent days.

The federal government would deploy “all the necessary human, material and technical resources” to support Kano state, Muhammadu Buhari said on Monday night.

Doctors in Kano say they have seen a surge in fatal cases of pneumonia. But local authorities have denied that Covid-19 is responsible, variously blaming malaria, meningitis, hypertension and other illnesses for the increased mortality.

By Monday evening there were only 32,138 reported cases of Covid-19 in Africa and 1,438 confirmed deaths.

However, limited testing facilities, combined with poor infrastructure and communications, means this is likely to be a significant underestimate of the true extent of the disease.

Local media reports from Kano of hundreds of deaths in recent days have raised the possibility of major outbreaks of the lethal disease going undetected for weeks across Africa.

A Lagos resident registers with the Red Cross before receiving food aid. Photograph: Sunday Alamba/AP

The World Health Organization has warned of 10m cases on the continent within three to six months, though experts say that the death toll could be lower if authorities are able to move swiftly to contain outbreaks of the disease.

“We are at the beginning in Africa,” Dr Mike Ryan, the executive director of the WHO’s Health Emergencies Programme, said last week.

In Nigeria, Africa’s most populous nation, the government has announced a strategy of “test, treat, trace and isolate” since detecting its first case on 27 February. The country currently has 1,182 cases and a national death toll of 35.

However, the strategy has been crippled by a lack of equipment. So far about 10,000 tests have been administered, mainly on people showing symptoms. On Saturday the Nigeria Centre for Disease Control’s director, Chikwe Ihekweazu, made an open plea for more kits to expand testing.

Kano state has become the centre of the pandemic in northern Nigeria, with 77 confirmed coronavirus cases and one death. The only test centre in Kano was closed from Wednesday to Sunday for disinfection after an outbreak of the disease there.

“Over the past week there have been reports of mysterious deaths in our great Kano state and I’m here to assure everyone that investigations are already ongoing. Autopsies are still being carried out but so far there’s been nothing to suggest that they are linked with Covid-19,” Abdullahi Umar Ganduje, the governor of Kano state, said on Monday.

Four members of the Kano government’s Covid-19 taskforce, including the co-chair, have already reportedly contracted the virus.

Neighbouring Kaduna state said it would extend a quarantine order by another month after the number of cases rose in Kano and the capital Abuja, and banned interstate travel, which it said was a major means of spreading the virus.

Ibrahim Musa, a medical doctor working at a federal hospital in Kano, described a sharp rise in cases of pneumonia over recent weeks, with widespread suspicions by medical personnel that the cases are linked to Covid-19.

“Pneumonia cases have been rising but that is not being recorded as Covid-19 because they are not testing. The pattern emerging widely is that elderly people are dying more. These deaths started happening when the lockdown was on the ground,” he said.

Burial of Abba Kyari, the chief of staff of the president of Nigeria, on 18 April. Photograph: Kola Sulaimon/AFP via Getty Images

Kano recorded its first case on 11 April. Since then, hospitals across the state have dramatically scaled down their services to ease up space in a severely overstretched health system and to protect medical staff from patients, now suspected of having Covid-19. All but emergency operations and treatment have been cancelled.

The shutdown of essential medical care has left millions of people with other health conditions at risk.

“Most of the hospitals in Kano have scaled down their activities. But when the services are down, and you need urgent treatment, it is hard because now emergency services are filled to capacity. So people are suffering from conditions they should be receiving treatment for but they can’t access the treatment. This is what we are seeing,” Musa said.

Khalil Muhammed, a driver in Kano city, said many people were scared. “Four of my neighbours have died, all in the last week, so we know the government are not understanding this thing. Two weeks ago in my area, people were burying, burying. I was thinking, what is this? I have been staying at home with my children and wife. What can I do? I know something is very wrong,” he said.

On Monday Buhari also said a lockdown covering the country’s Lagos and Abuja would be eased from 4 May.

Sani Aliyu, Nigeria’s national coordinator of the Covid-19 presidential task force, has said officials were keenly aware of the problems of lockdown in a country where many of the 200m inhabitants need to leave home every day to earn enough for basic subsistence.

To ease the threat of food shortages, the government has released huge quantities of grain from the national reserves, and distributed 100 trucks of rice across the country, along with approving conditional cash transfers.

But Aliyu admitted that such assistance was “probably going to be a drop in the ocean compared to what is needed”.