Police across swathes of Africa have failed to find more than a fraction of hundreds of people who have escaped from often unsanitary and uncomfortable Covid-19 quarantine centres in recent weeks.

There are more than 130,000 confirmed cases of Covid-19 in Africa, but low levels of testing means the true total is likely to be much higher.

In Malawi, more than 400 people repatriated from South Africa and elsewhere fled a makeshift centre set up at a stadium in Blantyre, the commercial capital, last week. Police and health workers told reporters they were unable to stop the escapees as they lacked adequate protective gear.

At least 46 escapees had tested positive for the virus, officials said. Some of those who fled told reporters they had bribed police. In separate incidents 26 people left the Mwanza border post while waiting for test results and eight others, all tested and shown to be infected, broke out of an isolation centre in Blantyre.

In Zimbabwe, Paul Nyathi, a police spokesman, said a total of 148 people had escaped from centres where a 21-day quarantine is mandatory for those returning from abroad.

“Security has been beefed up at the quarantine centres and measures are being taken to repair porous dura walls and security fences at some of the facilities,” Nyathi said.

There has also been at least one mass breakout in Kenya, while individuals have also escaped from quarantine in Gambia, Ghana, Nigeria, Uganda and Namibia.

Zimbabwe’s information minister, Monica Mutsvangwa, told reporters earlier this month that the government is increasing security at the schools, colleges and hotels used as quarantine centres. Government spokesman Nick Mangwana suggested that security officers guarding centres with high walls and razor wire might be receiving bribes to allow people to leave early.

Nearly all of Zimbabwe’s 75 new coronavirus cases last week came from centres that hold hundreds of people who have returned, sometimes involuntarily, from neighbouring South Africa and Botswana.

There have been widespread complaints about conditions in the quarantine centres, but the president, Emmerson Mnangagwa, said the returnees should not expect luxury.

“We can try to provide for them, but we cannot provide five-star facilities like hotels,” Mnangagwa said on Thursday.

Norman Matara, secretary general of the Zimbabwe Hospital Doctors Association, told the Guardian it was impossible to observe social distancing in the centres, which posed a significant risk to those held in them and to the country as a whole.

“It is disturbing. It may show that people are being infected in quarantine centres. So people should not share things like amenities and do not eat in overcrowded dining rooms,” Matara said.

South Africa, a developed economy which attracts migrant workers from across the region, has more than 27,000 confirmed cases of Covid-19 – the most in Africa. There are fears that the outbreak there could spread across southern Africa, where health systems are considerably less able to cope.

Zimbabwe’s government is also worried about people crossing porous borders illegally. The information ministry has set up a hotline number and is asking people to stop harbouring “border jumpers” and those who “abscond” from quarantine.

The busy border with South Africa was shut in March but there are close to 200 illegal crossing points used by traffickers to obtain basic goods that are unavailable or unaffordable in Zimbabwe.

Earlier this month, 41 Malawian immigrants were picked up by police after skipping the border from South Africa through the Limpopo River. Nine are being kept at a quarantine centre at the Beitbridge border point after they tested positive for Covid-19.

Sean Muguti, a freight clearing agent at Beitbridge, said smugglers were working with truckers: “It is a battle for survival … They will always find ways to beat the system.”

South Africa has been able to provide relatively comfortable quarantine facilities when necessary, hosting one group of nationals returning from China in a tourist lodge in the province of Limpopo.

But elsewhere centres are often unsanitary, uncomfortable and in some cases dangerous, human rights campaigners say.

In Kenya, investigations by Human Rights Watch revealed poor conditions, including lack of bedding, water, food, and cleaning supplies. People held in quarantine facilities told HRW they were not told of test results and that staff did not wear protective equipment.

A 22-year-old man who was quarantined following his arrival from France on 23 March told the organisation that his centre had lacked electricity, bathing water, food and water to drink.

“The beds had no mattresses or beddings. I slept on the spring bed with no mattress and nothing to cover myself. They told me I had to pay for water,” he said.

Many others described similar conditions in other facilities and said the authorities sometimes extended quarantine periods from the initial mandatory 14 days to more than 30 days, even when people tested negative several times.

All were asked to pay for accommodation, food and other costs before being allowed to leave. Many of those who could not pay were held for additional days and in one instance police were called in to beat those who persisted in pleading their inability to pay, victims and witnesses said.