Malawian police have carried out extrajudicial killings in a systematic campaign against hardcore criminals dubbed "operation elimination", according to a report released by a civil rights group.

The report was released Friday in Blantyre, the commercial capital of the poor southeast African country, by the Centre for Human Rights Education, Advice and Assistance (CHREAA).

The group's deputy director Chikondi Chijozi said Sunday the report had been handed over to the country's ombudsman Martha Chizuma for urgent action, but she said she had not yet received a copy.

"The findings of the research are quite alarming to us," Chijozi said. "We thought it would be important to submit it to the office of the ombudsman so that they do a thorough investigation to find out what happened to the 28 people that died under very suspicious circumstances."

Police spokesman James Kadadzera said he needed time to consult his superiors.

According to the report, there have been reports in recent years of extrajudicial killings by the Malawi police of former prisoners and those suspected, charged, tried or convicted of serious violent crimes including armed robbery in a systematic plan to eliminate hardcore criminals.

Chijozi told AFP that CHREAA conducted the study to investigate allegations of 43 alleged extrajudicial killings by the Malawi Police Service.

The names of the 43 were provided by an ex-prisoner who alleged that police had targeted him and three others for elimination. They survived "when the police aborted the mission after they discovered that there were people around" at the planned venue for the hit, she said.

According to Chijozi, three of the four were killed on a second attempt.

"The study found that 28 of the alleged victims were confirmed to have been shot by the police and died in very suspicious circumstances, three of whom were alleged to have died in a road accident but they also had gunshot wounds. One alleged victim was found alive," she said.

The study was undertaken in November and December 2018.

Chijozi said the report's findings were based on interviews with relatives and friends of the alleged victims and with some police officers.

In October, the police service came under fire after some officers were accused of sexually abusing women while quelling protests in the capital Lilongwe and in Msundwe, a trading outpost west of Lilongwe.

Barbara Banda, head of the Gender Coordination Network rights group, urged the authorities to "ensure thorough investigation into the... alleged rape, defilement and torture of innocent women and girls".

Malawi police set up a commission to investigate the allegations.