Romanus Pakure, deputy director of the government's National Aids Council, said the allegations were "a wake-up call" and that police were heading to the sites with health officials.
"I am shocked, the chairman of the council was shocked, we really need to investigate this and verify all these things," he said.
Social worker Margaret Marabe told reporters Monday that she saw three HIV infected men and two women buried alive by their relatives in remote villages when they became too sick to care for.
"They were crying and calling out their relatives' names and called for help," Marabe said on her return to the capital Port Moresby after spending five months in the Southern Highlands on an AIDS awareness campaign.
She said one called out "Mama, Mama" as the soil was being shovelled over his head.
Marabe works for a volunteer organisation called Igat Hope, Pidgin English for I've Got Hope, which supports people living with HIV/AIDS.
She said relatives of infected family members told her they had buried the victims because they were afraid of catching the disease themselves.
Papua New Guinea's fight against AIDS is hampered by its rugged terrain and a belief in witchcraft that is widespread in parts of the highlands, which had no contact with the outside world until the 1930s.
The AIDS council's Pakure said the reported killings might be connected to people's superstitions and their belief in sorcery.
"The people living in the coastal areas have got the message and they are not discriminating as much as before but it is a fact that (some) people still blame HIV infected people (saying) sorcery has been done on them," he said.
He admitted that the council's awareness and education programmes were not reaching everyone who need them.
Papua New Guinea faces one of the most serious HIV epidemics in the whole Asia-Pacific region. The first case was reported in 1987, and since then HIV prevalence has risen dramatically.
The disease is spread mainly through heterosexual intercourse in a country where polygamy is practised and rape and sexual violence are also common.
The official estimate is that two percent of PNG's six million people have contracted the AIDS virus, but non-governmental organisations and volunteer workers believe the figure is much higher.
Projected worst case scenarios of the epidemic see PNG suffering a 12.5 percent drop in its workforce and economic costs of 1.25 billion US dollars annually, according to the Australian government agency, AusAID.
The secretary of Igat Hope, Annie McPherson, said that efforts were being made to educate people in rural areas about the disease but the National Aids Council could not cope.
"The provincial offices are really struggling to get the right personnel and to have offices. There are a lot of offices that have been locked up because they cannot afford to meet their rent," she said.
McPherson backed Marabe's reports, saying she had heard of live burials happening in the past, attributing some at least to the mistaken belief that victims who have slipped into a coma are dead.
"There's no proper medical access available to be able to differentiate between some people who are in a coma and some people who are dead so we need to be able to get more services.
"It is a logistical nightmare to get services to people in the Highlands" she said.
PNG receives millions of dollars a year from donor countries to fight HIV, and the National AIDS Council was established by its parliament in December 1997 to oversee and coordinate the response.